REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
2003 Analog Devices, Inc. All rights reserved.
AD9882
Dual Interface for
Flat Panel Displays
FEATURES
Analog Interface
140 MSPS Maximum Conversion Rate
Programmable Analog Bandwidth
0.5 V to 1.0 V Analog Input Range
500 ps p-p PLL Clock Jitter at 140 MSPS
3.3 V Power Supply
Full Sync Processing
Midscale Clamping
4:2:2 Output Format Mode
Digital Interface
DVI 1.0 Compatible Interface
112 MHz Operation
High Skew Tolerance of 1 Full Input Clock
Sync Detect for "Hot Plugging"
Supports High Bandwidth Digital Content Protection
APPLICATIONS
RGB Graphics Processing
LCD Monitors and Projectors
Plasma Display Panels
Scan Converter
Microdisplays
Digital TV
FUNCTIONAL BLOCK DIAGRAM
A/D
CLAMP
R
AIN
8
R
OUT
A/D
CLAMP
G
AIN
8
G
OUT
A/D
CLAMP
B
AIN
8
B
OUT
ANALOG INTERFACE
SOGIN
HSYNC
FILT
VSYNC
SYNC
PROCESSING AND
CLOCK
GENERATION
MUXES
DATACK
HSOUT
VSOUT
SOGOUT
8
REF
REFBYPASS
R
OUT
8
G
OUT
8
B
OUT
DATACK
HSOUT
VSOUT
SOGOUT
DE
SCL
SERIAL REGISTER AND
POWER MANAGEMENT
SDA
A
0
DIGITAL INTERFACE
DVI
RECEIVER
HDCP
R
X0+
R
X0
R
X1+
R
X1
R
X2+
R
X2
R
XC+
R
XC
R
TERM
DDCSCL
DDCSDA
MCL
MDA
8
8
8
R
OUT
G
OUT
B
OUT
DATACK
DE
HSYNC
VSYNC
AD9882
GENERAL DESCRIPTION
The AD9882 offers designers the flexibility of an analog interface
and Digital Visual Interface (DVI) receiver integrated on a single
chip. Also included is support for High bandwidth Digital
Content Protection (HDCP).
Analog Interface
The AD9882 is a complete 8-bit 140 MSPS monolithic analog
interface optimized for capturing RGB graphics signals from
personal computers and workstations. Its 140 MSPS encode
rate capability and full power analog bandwidth of 300 MHz
supports resolutions up to SXGA (1280
1024 at 75 Hz).
The analog interface includes a 140 MHz triple ADC with
internal 1.25 V reference, a Phase Locked Loop (PLL), and
programmable gain, offset, and clamp control. The user provides
only a 3.3 V power supply, analog input, and Hsync. Three-
state CMOS outputs may be powered from 2.2 V to 3.3 V.
The AD9882's on-chip PLL generates a pixel clock from Hsync.
Pixel clock output frequencies range from 12 MHz to 140 MHz.
PLL clock jitter is typically 500 ps p-p at 140 MSPS. The AD9882
also offers full sync processing for composite sync and Sync-on-
Green (SOG) applications.
Digital Interface
The AD9882 contains a DVI 1.0 compatible receiver and supports
display resolutions up to SXGA (1280
1024 at 60 Hz). The
receiver features an intra-pair skew tolerance of up to one full
clock cycle.
With the inclusion of HDCP, displays may now receive encrypted
video content. The AD9882 allows for authentication of a video
receiver, decryption of encoded data at the receiver, and renew-
ability of that authentication during transmission as specified by
the HDCP v1.0 protocol.
Fabricated in an advanced CMOS process, the AD9882 is
provided in a space-saving 100-lead LQFP surface-mount plastic
package and is specified over the 0
C to 70C temperature range.
REV. A
AD9882SPECIFICATIONS
2
ANALOG INTERFACE
ELECTRICAL CHARACTERISTICS
Test
AD9882KST-100
AD9882KST-140
Parameter
Temp Level
Min
Typ
Max
Min
Typ
Max
Unit
RESOLUTION
8
8
Bits
DC ACCURACY
Differential Nonlinearity
25
C I
0.5
+1.25/1.0
0.5
+1.35/1.0 LSB
Full
VI
+1.35/1.0
+1.45/1.0 LSB
Integral Nonlinearity
25
C I
0.5
1.85
0.5
2.0
LSB
Full
VI
2.0
2.3
LSB
No Missing Codes
Full
VI
Guaranteed
Guaranteed
ANALOG INPUT
Input Voltage Range
Minimum
Full
VI
0.5
0.5
V p-p
Maximum
Full
VI
1.0
1.0
V p-p
Gain Tempco
25
C V
100
100
ppm/
C
Input Bias Current
Full
IV
1
1
mA
Input Full-Scale Matching
Full
VI
1.5
8.0
1.5
8.0
% FS
Offset Adjustment Range
Full
VI
46
49
56
46
49
56
% FS
REFERENCE OUTPUT
Output Voltage
Full
VI
1.20
1.25
1.32
1.20
1.25
1.32
V
Temperature Coefficient
Full
V
50
50
ppm/
C
SWITCHING PERFORMANCE
1
Maximum Conversion Rate
Full
VI
100
140
MSPS
Minimum Conversion Rate
Full
IV
10
10
MSPS
Data to Clock Skew
Full
IV
0.5
+2.0
0.5
+2.0
ns
Serial Port Timing
t
BUFF
Full
VI
4.7
4.7
ms
t
STAH
Full
VI
4.0
4.0
ms
t
DHO
Full
VI
0
0
ms
t
DAL
Full
VI
4.7
4.7
ms
t
DAH
Full
VI
4.0
4.0
ms
t
DSU
Full
VI
250
250
ns
t
STASU
Full
VI
4.7
4.7
ms
t
STOSU
Full
VI
4.0
4.0
ms
Hsync Input Frequency
Full
IV
15
110
15
110
kHz
Maximum PLL Clock Rate
Full
VI
100
140
MHz
Minimum PLL Clock Rate
Full
IV
12
12
MHz
PLL Jitter
25
C IV
500
700
2
500
700
2
ps p-p
Full
IV
1000
2
1000
2
ps p-p
Sampling Phase Tempco
Full
IV
15
15
ps/
C
DIGITAL INPUTS
Input Voltage, High (V
IH
)
Full
VI
2.6
2.6
V
Input Voltage, Low (V
IL
)
Full
VI
0.8
0.8
V
Input Current, High (I
IH
)
Full
IV
1.0
1.0
mA
Input Current, Low (I
IL
)
Full
IV
+1.0
+1.0
mA
Input Capacitance
25
C V
3
3
pF
DIGITAL OUTPUTS
1
Output Voltage, High (V
OH
)
Full
IV
V
DD
0.1
V
DD
0.1
V
Output Voltage, Low (V
OL
)
Full
IV
0.4
0.4
V
Duty Cycle, DATACK
Full
IV
45
50
55
45
50
55
%
Output Coding
Binary
Binary
(V
D
= 3.3 V, V
DD
= 3.3 V, ADC Clock = Maximum Conversion Rate, unless
otherwise noted.)
REV. A
AD9882
3
Test
AD9882KST-100
AD9882KST-140
Parameter
Temp Level
Min
Typ
Max
Min
Typ
Max
Unit
POWER SUPPLY
1
V
D
Supply Voltage
Full
IV
3.15
3.3
3.45
3.15
3.3
3.45
V
V
DD
Supply Voltage
Full
IV
2.2
3.3
3.6
2.20
3.3
3.6
V
PV
D
Supply Voltage
Full
IV
3.15
3.3
3.45
3.15
3.3
3.45
V
I
D
Supply Current (V
D
)
25
C V
162
181
mA
I
DD
Supply Current (V
DD
)
3
25
C V
47
63
mA
IPV
D
Supply Current (PV
D
)
25
C V
19
21
mA
Total Supply Current
Full
VI
228
237
265
274
mA
Power-Down Supply Current
Full
VI
30
35
30
35
mA
DYNAMIC PERFORMANCE
Analog Bandwidth, Full Power
25
C V
300
300
MHz
Signal-to-Noise Ratio (SNR)
25
C V
44
43
dB
f
IN
= 2.3 MHz
Crosstalk
Full
V
55
55
dBc
THERMAL CHARACTERISTICS
JA
Junction-to-Ambient
4
V
43
43
C/W
NOTES
1
Drive Strength = 11.
2
VCO Range = 10, Charge Pump Current = 110, PLL Divider = 1693.
3
DATACK Load = 15 pF, Data Load = 5 pF.
4
Simulated typical performance with package mounted to a four-layer board.
Specifications subject to change without notice.
REV. A
4
AD9882
DIGITAL INTERFACE
ELECTRICAL CHARACTERISTICS
Test
AD9882KST
Parameter
Conditions
Temp
Level
Min
Typ
Max
Unit
RESOLUTION
8
Bits
DC DIGITAL I/O Specifications
High Level Input Voltage (V
IH
)
Full
VI
2.6
V
Low Level Input Voltage (V
IL
)
Full
VI
0.8
V
High Level Output Voltage (V
OH
)
Full
IV
2.4
V
Low Level Output Voltage (V
OL
)
Full
IV
0.4
V
Output Leakage Current (I
OL
)
High Impedance
Full
IV
10
+10
mA
DC SPECIFICATIONS
Output High Drive
Output Drive = High
Full
V
11
mA
(I
OHD
)(V
OUT
= V
OH
)
Output Drive = Med
Full
V
8
mA
Output Drive = Low
Full
V
5
mA
Output Low Drive
Output Drive = High
Full
V
7
mA
(I
OLD
)(V
OUT
= V
OL
)
Output Drive = Med
Full
V
6
mA
Output Drive = Low
Full
V
5
mA
DATACK High Drive
Output Drive = High
Full
V
28
mA
(V
OHC
)(V
OUT
= V
OH
)
Output Drive = Med
Full
V
14
mA
Output Drive = Low
Full
V
7
mA
DATACK Low Drive
Output Drive = High
Full
V
15
mA
(V
OLC
)(V
OUT
= V
OL
)
Output Drive = Med
Full
V
9
mA
Output Drive = Low
Full
V
7
mA
Differential Input Voltage
Single-Ended Amplitude
Full
IV
75
800
mV
POWER SUPPLY
V
D
Supply Voltage
Full
IV
3.15
3.3
3.45
V
V
DD
Supply Voltage
Full
IV
2.2
3.3
3.6
V
PV
D
Supply Voltage
Full
IV
3.15
3.3
3.45
V
I
D
Supply Current (Typical Pattern)
1
25
C
V
269
mA
I
DD
Supply Current (Typical Pattern)
1, 2
25
C
V
32
mA
IPV
D
Supply Current (Typical Pattern)
1
25
C
V
54
mA
Total Supply Current with HDCP
(Typical Pattern)
1, 2
Full
IV
355
367
mA
I
D
Supply Current (Worst-Case Pattern)
3
25
C
V
276
mA
I
DD
Supply Current (Worst-Case Pattern)
2, 3
25
C
V
127
mA
IPV
D
Supply Current (Worst-Case Pattern)
3
25
C
V
54
mA
Total Supply Current with HDCP
(Worst-Case Pattern)
2, 3
Full
IV
457
468
mA
Power-Down Supply Current (I
PD
)
Full
VI
30
35
mA
(V
D
= 3.3 V, V
DD
= 3.3 V, Clock = Maximum, unless otherwise noted.)
REV. A
AD9882
5
Test
AD9882KST
Parameter
Conditions
Temp
Level
Min
Typ
Max
Unit
AC SPECIFICATIONS
Intra-Pair (+ to ) Differential
Input Skew (T
DPS
)
Full
IV
360
ps
Channel-to-Channel Differential
Full
IV
1
Clock
Input Skew (T
CCS
)
Period
Low-to-High Transition Time
for Data (D
LHT
)
Output Drive = High,
C
L
= 10 pF
Full
IV
2.2
ns
Output Drive = Med,
C
L
= 7 pF
Full
IV
2.5
ns
Output Drive = Low,
C
L
= 5 pF
Full
IV
3.2
ns
Low-to-High Transition Time for
DATACK (D
LHT
)
Output Drive = High,
C
L
= 10 pF
Full
IV
1.0
ns
Output Drive = Med,
C
L
= 7 pF
Full
IV
1.6
ns
Output Drive = Low,
C
L
= 5 pF
Full
IV
2.1
ns
High-to-Low Transition Time for
Data (D
HLT
)
Output Drive = High,
C
L
= 10 pF
Full
IV
2.2
ns
Output Drive = Med,
C
L
= 7 pF
Full
IV
1.9
ns
Output Drive = Low,
C
L
= 5 pF
Full
IV
1.7
ns
High-to-Low Transition Time for
DATACK (D
HLT
)
Output Drive = High,
C
L
= 10 pF
Full
IV
1.0
ns
Output Drive = Med,
C
L
= 7 pF
Full
IV
1.0
ns
Output Drive = Low,
C
L
= 5 pF
Full
IV
1.4
ns
Data-to-Clock Skew
4
Full
IV
0.5
+2.0
ns
Duty Cycle, DATACK
4
Full
IV
40
46
50
%
DATACK Frequency (F
CIP
)
Full
VI
25
112
MHz
NOTES
1
The typical pattern contains a grayscale area, Output Drive = High.
2
DATACK Load = 10 pF, Data Load = 10 pF.
3
The worst-case pattern contains a black and white checkerboard pattern, Output Drive = High.
4
DRIVE STRENGTH = 11
Specifications subject to change without notice.
REV. A
6
AD9882
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although the
AD9882 features proprietary ESD protection circuitry, permanent damage may occur on devices
subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended
to avoid performance degradation or loss of functionality.
ORDERING GUIDE
Temperature
Package
Model
Range
Option
AD9882KST-100
0
C to 70C
ST-100
AD9882KST-140
0
C to 70C
ST-100
AD9882/PCB
25
C
Evaluation Board
ABSOLUTE MAXIMUM RATINGS
*
V
D
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 V
V
DD
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 V
Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . V
D
to 0.0 V
VREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
D
to 0.0 V
Digital Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 V to 0.0 V
Digital Output Current . . . . . . . . . . . . . . . . . . . . . . . . 20 mA
Operating Temperature . . . . . . . . . . . . . . . . 25
C to +85C
Storage Temperature . . . . . . . . . . . . . . . . . 65
C to +150C
Maximum Junction Temperature . . . . . . . . . . . . . . . . 175
C
Maximum Case Temperature . . . . . . . . . . . . . . . . . . . 150
C
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating; functional operation of the device
at these or any other conditions outside of those indicated in the operation sections
of this specification is not implied. Exposure to absolute maximum ratings for
extended periods may affect device reliability.
EXPLANATION OF TEST LEVELS
Test Level
I.
100% production tested.
II.
100% production tested at 25
C and sample tested at
specified temperatures.
III. Sample tested only.
IV.
Parameter is guaranteed by design and characterization
testing.
V.
Parameter is a typical value only.
VI.
100% production tested at 25
C; guaranteed by design
and characterization testing.
REV. A
AD9882
7
PIN CONFIGURATION
1
GND
GREEN<7>
GREEN<6>
GREEN<5>
GREEN<4>
GREEN<3>
GREEN<2>
GREEN<1>
GREEN<0>
V
DD
GND
BLUE<7>
BLUE<6>
BLUE<5>
BLUE<4>
BLUE<3>
BLUE<2>
BLUE<1>
BLUE<0>
V
DD
GND
CTL 0
CTL 1
CTL 2
CTL 3
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
GND
V
D
R
TERM
V
D
V
D
GND
R
X0
R
X0+
GND
R
X1
R
X1+
GND
R
X2
R
X2+
GND
R
XC+
R
XC
V
D
PV
D
GND
P
VD
GND
FIL
T
P
VD
GND
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
75
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
GND
MIDBYPASS
REFBYPASS
V
D
GND
RAIN
V
D
GND
V
D
GND
GAIN
SOGIN
V
D
GND
V
D
GND
BAIN
V
D
GND
V
D
GND
DDCSDA
DDCSCL
P
VD
GND
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
80
79
78
77
76
TOP VIEW
(Not to Scale)
AD9882
V
DD
RED<0>
RED<1>
RED<2>
RED<3>
RED<4>
RED<5>
RED<6>
RED<7>
GND
SOGOUT
HSOUT
VSOUT
DE
DA
T
A
C
K
GND
MD
A
MCL
VSYNC
HSYNC
SD
A
SCL
A0
V
DD
V
DD
REV. A
8
AD9882
Table I. Complete Pinout List
Pin
Pin
Type
Mnemonic
Function
Value
Number Interface
Analog
R
AIN
Analog Input for Converter R
0.0 V to 1.0 V
70
Analog
Video Inputs G
AIN
Analog Input for Converter G
0.0 V to 1.0 V
65
Analog
B
AIN
Analog Input for Converter B
0.0 V to 1.0 V
59
Analog
External
HSYNC
Horizontal Sync Input
3.3 V CMOS
79
Analog
Sync/Clock
VSYNC
Vertical Sync Input
3.3 V CMOS
80
Analog
SOGIN
Input for Sync-on-Green
0.0 V to 1.0 V
64
Analog
Sync
HSOUT
HSYNC Output Clock (Phase-Aligned with DATACK) 3.3 V CMOS
88
Both
Outputs
VSOUT
VSYNC Output Clock
3.3 V CMOS
87
Both
SOGOUT
Sync-on-Green Slicer Output
3.3 V CMOS
89
Analog
References
REFBYPASS
Internal Reference Bypass
1.25 V
73
Analog
MIDBYPASS Internal Midscale Voltage Bypass
74
Analog
PLL Filter
FILT
Connection for External Filter Components for
48
Analog
Internal PLL
Power
V
D
Analog Power Supply
3.15 V to 3.45 V
Both
Supply
V
DD
Output Power Supply
2.2 V to 3.6 V
Both
PV
D
PLL Power Supply
3.15 V to 3.45 V
Both
GND
Ground
0 V
Both
Serial Port
SDA
Serial Port Data I/O
3.3 V CMOS
78
Both
Control
SCL
Serial Port Data Clock (100 kHz Max)
3.3 V CMOS
77
Both
A0
Serial Port Address Input
3.3 V CMOS
76
Both
Data
Red [7:0]
Outputs of Converter "Red", Bit 7 is the MSB
3.3 V CMOS
9299
Both
Outputs
Green [7:0]
Outputs of Converter "Green", Bit 7 is the MSB
3.3 V CMOS
29
Both
Blue [7:0]
Outputs of Converter "Blue", Bit 7 is the MSB
3.3 V CMOS
1219
Both
Data Clock
Output
DATACK
Data Output Clock for the Analog and Digital Interface
3.3 V CMOS
85
Both
Digital Video R
X0+
Digital Input Channel 0 True
33
Digital
Data Inputs
R
X0
Digital Input Channel 0 Complement
32
Digital
R
X1+
Digital Input Channel 1 True
36
Digital
R
X1
Digital Input Channel 1 Complement
35
Digital
R
X2+
Digital Input Channel 2 True
39
Digital
R
X2
Digital Input Channel 2 Complement
38
Digital
Digital Video R
XC+
Digital Data Clock True
41
Digital
Clock Inputs R
XC
Digital Data Clock Complement
42
Digital
Data Enable DE
Data Enable
3.3 V CMOS
86
Digital
Control Bits
CTL [0:3]
Decoded Control Bits
3.3 V CMOS
2225
Digital
R
TERM
R
TERM
Sets Internal Termination Resistance
28
Digital
HDCP
DDCSCL
HDCP Slave Serial Port Data Clock
3.3 V CMOS
53
Digital
DDCSDA
HDCP Slave Serial Port Data I/O
3.3 V CMOS
54
Digital
MCL
HDCP Master Serial Port Data Clock
3.3 V CMOS
81
Digital
MDA
HDCP Master Serial Port Data I/O
3.3 V CMOS
82
Digital
REV. A
AD9882
9
PIN DESCRIPTIONS OF SHARED PINS BETWEEN
ANALOG AND DIGITAL INTERFACES
HSOUT
Horizontal Sync Output
A reconstructed and phase-aligned version of the
video Hsync. The polarity of this output can be
controlled via a serial bus bit. In analog interface
mode, the placement and duration are variable.
In digital interface mode, the placement and
duration are set by the graphics transmitter.
VSOUT
Vertical Sync Output
The separated Vsync from a composite signal or
a direct pass-through of the Vsync input. The
polarity of this output can be controlled via a
serial bus bit. The placement and duration in all
modes is set by the graphics transmitter.
SERIAL PORT (2-WIRE)
SDA
Serial Port Data I/O
SCL
Serial Port Data Clock
A0
Serial Port Address Input
For a full description of the 2-wire serial register,
refer to the Control Port section on 2-Wire
Serial Control.
DATA OUTPUTS
RED
Data Output, RED Channel
GREEN
Data Output, GREEN Channel
BLUE
Data Output, BLUE Channel
The main data outputs. Bit 7 is the MSB. These
outputs are shared between the two interfaces
and behave according to which interface is active.
Refer to the sections on the two interfaces for
more information on how these outputs behave.
DATACK
Data Output Clock
Just like the data outputs, the data clock output
is shared between the two interfaces. It behaves
differently depending on which interface is active.
Refer to the sections on the two interfaces to
determine how this pin behaves.
Table II. Analog Interface Pin List
Pin
Pin Type
Mnemonic
Function
Value
Number
Analog Video
R
AIN
Analog Input for Converter R
0.0 V to 1.0 V
70
Inputs
G
AIN
Analog Input for Converter G
0.0 V to 1.0 V
65
B
AIN
Analog Input for Converter B
0.0 V to 1.0 V
59
External
HSYNC
Horizontal SYNC Input
3.3 V CMOS
79
Sync/Clock
VSYNC
Vertical SYNC Input
3.3 V CMOS
80
SOGIN
Sync-on-Green Input
0.0 V to 1.0 V
64
Sync Outputs
HSOUT
Hsync Output (Phase-Aligned with DATACK)
3.3 V CMOS
88
VSOUT
Vsync Output
3.3 V CMOS
87
SOGOUT
Composite SYNC
3.3 V CMOS
89
Voltage
REFBYPASS
Internal Reference Bypass
1.25 V
73
Reference
MIDBYPASS
Internal Midscale Voltage Bypass
74
Clamp Voltages
PLL Filter
FILT
Connection for External Filter Components for Internal PLL
48
Power Supply
V
D
Main Power Supply
3.15 V to 3.45 V
PV
D
PLL Power Supply (Nominally 3.3 V)
3.15 V to 3.45 V
V
DD
Output Power Supply
2.2 V to 3.6 V
GND
Ground
0 V
REV. A
10
AD9882
PIN FUNCTION DETAIL (ANALOG INTERFACE)
INPUTS
R
AIN
Analog Input for RED Channel
G
AIN
Analog Input for GREEN Channel
B
AIN
Analog Input for BLUE Channel
High impedance inputs that accept the RED,
GREEN, and BLUE channel graphics signals,
respectively. For RGB, the three channels are
identical and can be used for any colors, but
colors are assigned for convenient reference.
For proper 4:2:2 formatting in a YPbPr application,
the Y must be connected to the G
AIN
input, the
Pb must be connected to the B
AIN
input, and the
Pr must be connected to the R
AIN
input.
They accommodate input signals ranging from
0.5 V to 1.0 V full scale. Signals should be
ac-coupled to these pins to support clamp
operation.
HSYNC
Horizontal Sync Input
This input receives a logic signal that establishes
the horizontal timing reference and provides the
frequency reference for pixel clock generation.
The logic sense of this pin is controlled by Serial
Register Bit 10H, Bit 6 (Hsync Polarity). Only
the leading edge of Hsync is active; the trailing
edge is ignored. When Hsync Polarity = 0, the
falling edge of Hsync is used. When Hsync
Polarity = 1, the rising edge is active.
The input includes a Schmitt trigger for noise
immunity, with a nominal input threshold of
1.5 V.
Electrostatic Discharge (ESD) protection diodes
will conduct heavily if this pin is driven more
than 0.5 V above the maximum tolerance voltage
(3.3 V), or more than 0.5 V below ground.
VSYNC
Vertical Sync Input
This is the input for vertical sync.
SOGIN
Sync-on-Green Input
This input is provided to assist with processing
signals with embedded sync, typically on the
GREEN channel. The pin is connected to a
high speed comparator with an internally gener-
ated threshold, which is set by the value of
register 0FH, Bits 73.
When connected to an ac-coupled graphics
signal with embedded sync, it will produce a
noninverting digital output on SOGOUT.
When not used, this input should be left uncon-
nected. For more details on this function and
how it should be configured, refer to the Sync-
on-Green section.
SOGOUT
Sync-on-Green Slicer Output
This pin can be programmed to produce either
the output from the Sync-on-Green slicer com-
parator or an unprocessed but delayed version of
the Hsync input. See the Sync Processing Block
Diagram, Figure 18, to view how this pin is
connected.
Note: The output from this pin is the composite
SYNC without additional processing from the
AD9882.
FILT
External Filter Connection
For proper operation, the pixel clock generator
PLL requires an external filter. Connect the
filter shown in Figure 6 to this pin. For optimal
performance, minimize noise and parasitics on
this node.
REFBYPASS Internal Reference BYPASS
Bypass for the internal 1.25 V band gap refer-
ence. It should be connected to ground through
a 0.1
mF capacitor.
The absolute accuracy of this reference is
4%,
and the temperature coefficient is
50 ppm,
which is adequate for most AD9882 applica-
tions. If higher accuracy is required, an external
reference may be employed instead.
MIDBYPASS Midscale Voltage Reference BYPASS
Bypass for the internal midscale voltage refer-
ence. It should be connected to ground through
a 0.1
mF capacitor. The exact voltage varies with
the gain setting of the RED channel.
HSOUT
Horizontal Sync Output
A reconstructed and phase-aligned version of
the Hsync input. The duration of Hsync can
only be programmed on the analog interface,
not the digital.
DATACK
Data Output Clock
The data clock output signal is used to clock the
output data and HSOUT into external logic.
It is produced by the internal clock generator
and is synchronous with the internal pixel
sampling clock.
When the sampling time is changed by adjusting
the PHASE register, the output timing is shifted
as well. The Data, DATACK, and HSOUT
outputs are all moved so the timing relationship
among the signals is maintained.
VSOUT
Vertical Sync Output
The separated Vsync from a composite signal or
a direct pass-through of the Vsync input. The
polarity of this output can be controlled via
Register 10H, Bit 2. The placement and duration
in all modes is set by the graphics transmitter.
REV. A
AD9882
11
RED
Data Output, RED Channel
GREEN
Data Output, GREEN Channel
BLUE
Data Output, BLUE Channel
These are the main data outputs. Bit 7 is the MSB.
The delay from pixel sampling time to output is
fixed. When the sampling time is changed by
adjusting the PHASE register, the output timing
is shifted as well. The DATACK and HSOUT
outputs are also moved, so the timing relation-
ship among the signals is maintained.
Please refer to the timing diagrams for more
information.
POWER SUPPLY
V
D
Main Power Supply
These pins supply power to the main elements of
the circuit. They should be as quiet as possible.
V
DD
Digital Output Power Supply
A large number of output pins (up to 25) switch-
ing at high speed (up to 140 MHz) generates a
lot of power supply transients. These supply
pins are identified separately from the V
D
pins
so special care can be taken to minimize out-
put noise transferred into the sensitive analog
circuitry.
If the AD9882 is interfacing with lower voltage
logic, V
DD
may be connected to a lower supply
voltage (as low as 2.2 V) for compatibility.
PV
D
Clock Generator Power Supply
The most sensitive portion of the AD9882 is the
clock generation circuitry. These pins provide
power to the clock PLL and help the user design
for optimal performance. The designer should
provide noise-free power to these pins.
GND
Ground
The ground return for all circuitry on chip. It is
recommended that the AD9882 be assembled on
a single solid ground plane, with careful attention
to ground current paths.
Table III. Interface Selection Controls
Analog
Digital
AIO
Interface
Interface
AIS
Active
(0FH Bit 2)
Detect
Detect
(0FH Bit 1)
Interface
Description
1
X
X
0
Analog
Force the analog interface active.
1
Digital
Force the digital interface active.
0
0
X
None
Neither interface was detected. Both interfaces are
powered down.
0
1
X
Digital
The digital interface was detected. Power down the
analog interface.
1
0
X
Analog
The analog interface was detected. Power down the
digital interface.
1
1
0
Analog
Both interfaces were detected. The analog interface
gets priority.
1
Digital
Both interfaces were detected. The digital interface
gets priority.
0
REV. A
12
AD9882
Table IV. Power-Down Modes, 4:2:2 and 4:4:4 Format Descriptions
Analog
Digital
Active
Active
Power- Interface
Interface
Interface
Interface
4:2:2
Mode
Down
1
Detect
2
Detect
3
Override
Select
Formatting Data Sheet Signals Powered On
Soft Power-
1
0
0
0
X
X
Serial bus, digital interface clock detect,
Down (Seek
analog interface clock detect, SOG
Mode)
Digital
1
0
1
0
X
X
Serial bus; digital interface and analog
Interface On
interface activity detect; SOG, band gap
reference; red, green, and blue outputs
Analog
1
1
0
0
X
0
Serial bus; analog interface and digital
Interface On
interface clock detect; SOG, band gap
4:4:4 Format
reference; red, green, and blue outputs
Analog
1
1
0
0
X
1
Serial bus; analog interface and digital
Interface On
interface clock detect; SOG, band gap
4:2:2 Format
reference; red and green outputs only
Serial Bus
1
1
1
1
0
0
Same as Analog Interface
Arbitrated
on 4:4:4 Mode
Interface
Serial Bus
1
1
1
1
0
1
Same as Analog Interface
Arbitrated
on 4:2:2 Mode
Interface
Serial Bus
1
1
1
1
1
X
Same as Digital Interface Mode
Arbitrated
Interface
Override to
1
1
X
1
0
0
Same as Analog Interface
Analog
4:4:4 Mode
Interface
Override to
1
1
X
1
0
1
Same as Analog Interface
Analog
4:2:2 Mode
Interface
Override to
1
X
1
1
1
X
Same as Digital Interface Mode
Digital
Interface
Absolute
0
X
X
X
X
X
Serial Bus
Power-
Down
NOTES
1
Power-down is controlled via Bit 1 in Serial Bus Register 14H.
2
Analog Interface Detect is determined by OR-ing Bits 7, 6, and 5 in Serial Bus Register 15H.
3
Digital Interface Detect is determined by Bit 4 in Serial Bus Register 15H.
REV. A
AD9882
13
THEORY OF OPERATION (INTERFACE DETECTION)
Active Interface Detection and Selection
The AD9882 includes circuitry to detect whether an interface is
active or not. See Table III.
For detecting the analog interface, the circuitry monitors the
presence of Hsync, Vsync, and Sync-on-Green. The result of
the detection circuitry can be read from the 2-wire serial inter-
face bus at Address 15H, Bits 7, 5, and 6, respectively. If one of
these sync signals disappears, the maximum time it takes for the
circuitry to detect it is 100 ms.
For detecting the digital interface, there are two stages of detection.
The first stage searches for the presence of the digital interface
clock. The circuitry for detecting the digital interface clock is
active even when the digital interface is powered down. The
result of this detection stage can be read from the 2-wire serial
interface bus at Address 15H, Bit 4. If the clock disappears, the
maximum time it takes for the circuitry to detect it is 100 ms.
Once a digital interface clock is detected, the digital interface is
powered up and the second stage of detection begins. During
the second stage, the circuitry searches for 32 consecutive DEs.
Once 32 DEs are found, the detection process is complete.
There is an override for the automatic interface selection. It is
the AIO (Active Interface Override) bit, Register 0FH, Bit 2.
When the AIO bit is set to logic "0," the automatic circuitry will
be used. When the AIO bit is set to logic "1," the AIS (Active
Interface Select) bit (Register 0FH, Bit 1) will be used to
determine the active interface rather than the automatic circuitry.
Power Management
The AD9882 is a dual interface device with shared outputs. Only
one interface can be used at a time. For this reason, the chip auto-
matically powers down the unused interface. When the analog
interface is being used, most of the digital interface circuitry is
powered down, and vice versa. This helps to minimize the AD9882
total power dissipation. In addition, if neither interface has activity
on it, then the chip powers down both interfaces. The AD9882
uses the activity detect circuits, the active interface bits in Serial
Register 15H, the active interface override bits in Register 0FH,
Bits 2 and 1, and the power-down bit in Register 14H, Bit 1, to
determine the correct power state. In a given power mode, not all
circuitry in the inactive interface is powered down completely.
When the digital interface is active, the band gap reference
Hsync, Vsync, and SOG detect circuitry remain powered up.
When the analog interface is active, the digital interface clock
detect circuit is not powered down. Table IV summarizes how
the AD9882 determines what power mode to be in and what
circuitry is powered on/off in each of these modes. The power-
down command has priority, then the active interface override,
and then the automatic circuitry.
THEORY OF OPERATION AND DESIGN GUIDE
(ANALOG INTERFACE)
General Description
The AD9882 is a fully integrated solution for capturing analog
RGB signals and digitizing them for display on flat panel
monitors or projectors. The device is ideal for implementing a
computer interface for HDTV monitors or as the front end to
high performance video scan converters.
Implemented in a high performance CMOS process, the inter-
face can capture signals with pixel rates of up to 140 MHz.
The AD9882 includes all necessary input buffering, signal dc
restoration (clamping), offset and gain (brightness and contrast)
adjustment, pixel clock generation, sampling phase control, and
output data formatting. All controls are programmable via a
2-wire serial interface. Full integration of these sensitive analog
functions makes the system design straightforward and less
sensitive to the physical and electrical environment.
With a typical power dissipation of only 875 mW and an operat-
ing temperature range of 0
C to 70C, the device requires no
special environmental considerations.
Input Signal Handling
The AD9882 has three high impedance analog input pins for
the RED, GREEN, and BLUE channels. They will accommodate
signals ranging from 0.5 V to 1.0 V p-p.
Signals are typically brought onto the interface board via a
DVI-I connector, a 15-pin D connector, or BNC connectors.
The AD9882 should be located as close as practical to the input
connector. Signals should be routed via matched-impedance
traces (normally 75
W) to the IC input pins.
At that point, the signal should be resistively terminated (75
W
to the signal ground return) and capacitively coupled to the
AD9882 inputs through 47 nF capacitors. These capacitors
form part of the dc restoration circuit. See Figure 1.
In an ideal world of perfectly matched impedances, the best
performance can be obtained with the widest possible signal band-
width. The wide bandwidth inputs of the AD9882 (300 MHz) can
track the input signal continuously as it moves from one pixel
level to the next and digitize the pixel during a long, flat pixel
time. In many systems, however, there are mismatches, reflections,
and noise, which can result in excessive ringing and distortion of
the input waveform. This makes it more difficult to establish a
sampling phase that provides good image quality. It has been
shown that a small inductor in series with the input is effective
in rolling off the input bandwidth slightly and providing a high
quality signal over a wider range of conditions. Using a Fair-Rite
#2508051217Z0 High Speed Signal Chip Bead inductor in the
circuit of Figure 1 gives good results in most applications.
RGB
INPUT
R
AIN
G
AIN
B
AIN
47nF
75
Figure 1. Analog Input Interface Circuit
REV. A
14
AD9882
Hsync, Vsync Inputs
The AD9882 receives a horizontal sync signal and uses it to
generate the pixel clock and clamp timing. This can be either a
sync signal directly from the graphics source or a preprocessed
TTL or CMOS level signal.
The Hsync input includes a Schmitt trigger buffer and is capable
of handling signals with long rise times, with superior noise
immunity. In typical PC based graphic systems, the sync signals
are simply TTL level drivers feeding unshielded wires in the
monitor cable. As such, no termination is required.
Serial Control Port
The serial control port is designed for 3.3 V logic. If there are
5 V drivers on the bus, these pins should be protected with
150
W series resistors placed between the pull-up resistors and
the input pins.
Output Signal Handling
The digital outputs are designed and specified to operate from
a 3.3 V power supply (V
DD
). They can also work with a V
DD
as
low as 2.5 V for compatibility with other 2.5 V logic.
Clamping
RGB Clamping
To properly digitize the incoming signal, the dc offset of the
input must be adjusted to fit the range of the on-board A/D
converters.
Most graphics systems produce RGB signals with black at ground
and white at approximately 0.75 V. However, if sync signals are
embedded in the graphics, the sync tip is often at ground and
black is at 300 mV; white will be approximately 1.0 V. Some
common RGB line amplifier boxes use emitter-follower buffers
to split signals and increase drive capability. This introduces a
700 mV dc offset to the signal, which is removed by clamping
for proper capture by the AD9882.
The key to clamping is to identify a portion (time) of the signal
when the graphic system is known to be producing black. Origi-
nating from CRT displays, the electron beam is "blanked" by
sending a black level during horizontal retrace to prevent
disturbing the image. Most graphics systems maintain this
format of sending a black level between active video lines.
An offset is then introduced, which results in the A/D converters
producing a black output (code 00H) when the known black
input is present. The offset then remains in place when other
signal levels are processed, and the entire signal is shifted to
eliminate offset errors.
In systems with embedded sync, a blacker-than-black signal
(Hsync) is produced briefly to signal the CRT that it is time to
begin a retrace. For obvious reasons, it is important to avoid
clamping on the tip of Hsync. Fortunately, there is virtually always
a period following Hsync called the back porch, in which a good
black reference is provided. This is the time when clamping should
be done.
The clamp timing is established by the AD9882 internal clamp
timing generator. The Clamp Placement Register (05H) is
programmed with the number of pixel times that should pass
after the trailing edge of Hsync before clamping starts. A second
register (Clamp Duration, 06H) sets the duration of the clamp.
These are both 8-bit values, providing considerable flexibility in
clamp generation. The clamp timing is referenced to the trailing
edge of Hsync since the back porch (black reference) always
follows Hsync. A good starting point for establishing clamping is
to set the clamp placement to 08H (providing eight pixel periods
for the graphics signal to stabilize after sync) and set the clamp
duration to 14H (giving the clamp 20 pixel periods to re-establish
the black reference).
The value of the external input coupling capacitor affects the
performance of the clamp. If the value is too small, there can be
an amplitude change during a horizontal line time (between
clamping intervals). If the capacitor is too large, then it will take
excessively long for the clamp to recover from a large change in
incoming signal offset. The recommended value (47 nF) results
in recovery from a step error of 100 mV to within one-half LSB
in 10 lines using a clamp duration of 20 pixel periods on a 75 Hz
SXGA signal.
YUV Clamping
YUV signals are slightly different from RGB signals in that the
dc reference level (black level in RGB signals) will be at the
midpoint of the U and V video. For these signals, it can be
necessary to clamp to the midscale range of the A/D converter
range (80H) rather than the bottom of the A/D converter range (00H).
Clamping to midscale rather than ground can be accomplished
by setting the clamp select bits in the serial bus register. Each of
the three converters has its own selection bit so that they can be
clamped to either midscale or ground independently. These bits
are located in Register 11H and are Bits 46. The midscale
reference voltage that each A/D converter clamps to is provided
on the MIDBYPASS pin (Pin 74). This pin should be bypassed
to ground with a 0.1
mF capacitor (even if midscale clamping is
not required).
Gain and Offset Control
The AD9882 can accommodate input signals with inputs ranging
from 0.5 V to 1.0 V full scale. The full-scale range is set in three
8-bit registers (RED Gain, GREEN Gain, and BLUE Gain).
A code of 0 establishes a minimum input range of 0.5 V;
255 corresponds with the maximum range of 1.0 V. Note
that INCREASING the gain setting results in an image with
LESS contrast.
The offset control shifts the entire input range, resulting in a
change in image brightness. Three 7-bit registers (RED Offset,
GREEN Offset, BLUE Offset) provide independent settings
for each channel.
The offset controls provide a
63 LSB adjustment range. This
range is connected with the full-scale range, so if the input range
is doubled (from 0.5 V to 1.0 V), the offset step size is also
doubled (from 2 mV per step to 4 mV per step).
Figure 2 illustrates the interaction of gain and offset controls.
The magnitude of an LSB in offset adjustment is proportional to
the full-scale range, so changing the full-scale range also changes
the offset. The change is minimal if the offset setting is near
midscale. When changing the offset, the full-scale range is not
affected, but the full-scale level is shifted by the same amount as
the zero-scale level.
REV. A
AD9882
15
1.0 V
0.5 V
0.0 V
INPUT RANGE
GAIN
00H
FFH
OFFSET = 3FH
OFFSET = 7FH
OFFSET = 00H
OFFSET = 3FH
OFFSET = 7FH
OFFSET = 00H
Figure 2. Gain and Offset Control
Sync-on-Green (SOG)
The Sync-on-Green input operates in two steps. First, it sets
a baseline clamp level off of the incoming video signal with a
negative peak detector. Second, it sets the Sync trigger level
(nominally 150 mV above the negative peak). The exact trigger
level is variable and can be programmed via Register 0FH,
Bits 73. The Sync-on-Green input must be ac-coupled to the
green analog input through its own capacitor as shown in Figure 3.
The value of the capacitor must be 1 nF
20%. If Sync-on-Green
is not used, this connection is not required and SOGIN should
be left unconnected. (Note: The Sync-on-Green signal is always
negative polarity.) Please refer to the Sync Processing section
for further information.
47nF
47nF
47nF
R
AIN
B
AIN
G
AIN
SOGIN
1nF
Figure 3. Typical Clamp Configuration
Clock Generation
A Phase Locked Loop (PLL) is employed to generate the pixel
clock. The Hsync input provides a reference frequency for the
PLL. A Voltage Controlled Oscillator (VCO) generates a much
higher pixel clock frequency. This pixel clock is divided by the
PLL divide value (Registers 01H and 02H) and phase compared
with the Hsync input. Any error is used to shift the VCO frequency
and maintain lock between the two signals.
The stability of this clock is a very important element in provid-
ing the clearest and most stable image. During each pixel time,
there is a period during which the signal is slewing from the old
pixel amplitude and settling at its new value. Then there is a
time when the input voltage is stable, before the signal must
slew to a new value (Figure 4). The ratio of the slewing time to
the stable time is a function of the bandwidth of the graphics
DAC and the bandwidth of the transmission system (cable and
termination). It is also a function of the overall pixel rate. Clearly,
if the dynamic characteristics of the system remain fixed, then
the slewing and settling time is likewise fixed. This time must be
subtracted from the total pixel period, leaving the stable period.
At higher pixel frequencies, the total cycle time is shorter, and
the stable pixel time becomes shorter as well.
PIXEL CLOCK
INVALID SAMPLE TIMES
Figure 4. Pixel Sampling Times
Any jitter in the clock reduces the precision with which the
sampling time can be determined and must also be subtracted
from the stable pixel time.
Considerable care has been taken in the design of the AD9882's
clock generation circuit to minimize jitter. As indicated in Fig-
ure 5, the clock jitter of the AD9882 is less than 6% of the total
pixel time in all operating modes, making the reduction in the
valid sampling time due to jitter negligible.
8
0
135.0
25.1 31.5 36.0 40.0
85.5
4
50.0 56.2 65.0 75.0 78.7
94.5 108.0
10
6
2
PIXEL CLOCK FREQUENCY MHz
PI
XEL CLOCK JITTER (p-p) %
Figure 5. Pixel Clock Jitter vs. Frequency
REV. A
16
AD9882
Table V. VCO Frequency Ranges
PV1
PV0
Pixel Clock Range (MHz)
0
0
1241
0
1
4182
1
0
82140
3. The 3-bit Charge Pump Current Register (Register 03H,
Bits 35). This register allows the current that drives the
low-pass loop filter to be varied. The possible current values
are listed in Table VI.
Table VI. Charge Pump Current/Control Bits
Ip2
Ip1
Ip0
Current (
m
A)
0
0
0
50
0
0
1
100
0
1
0
150
0
1
1
250
1
0
0
350
1
0
1
500
1
1
0
750
1
1
1
1500
4. The 5-bit Phase Adjust Register (Register 04H, Bits 37).
The phase of the generated sampling clock may be shifted to
locate an optimum sampling point within a clock cycle. The
Phase Adjust Register provides 32 phase-shift steps of 11.25
each. The Hsync signal with an identical phase shift is available
through the HSOUT pin.
The PLL characteristics are determined by the loop filter design,
the PLL charge pump current, and the VCO range setting.
The loop filter design is illustrated in Figure 6. Recommended
settings of VCO range and charge pump current for VESA
standard display modes are listed in Table VII.
P
VD
C
Z
0.082 F
R
Z
2.74k
C
P
0.0082 F
FILT
Figure 6. PLL Loop Filter Detail
Four programmable registers are provided to optimize the
performance of the PLL. These registers are:
1. The 12-bit Divisor Register (Registers 01H and 02H). The
input Hsync frequencies range from 15 kHz to 110 kHz. The
PLL multiplies the frequency of the Hsync signal, producing
pixel clock frequencies in the range of 12 MHz to 140 MHz.
The Divisor Register controls the exact multiplication factor.
This register may be set to any value between 221 and 4095.
(The divide ratio that is actually used is the programmed
divide ratio plus one.)
2. The 2-bit VCO Range Register (Register 03H, Bits 6 and 7).
To improve the noise performance of the AD9882, the VCO
operating frequency range is divided into three overlapping
regions. The VCO Range register sets this operating range.
The frequency ranges for the lowest and highest regions are
shown in Table V.
Table VII. Recommended VCO Range and Charge Pump Current Settings for Standard Display Formats
Refresh
Horizontal
Standard
Resolution
Rate (Hz)
Frequency (kHz)
Pixel Rate (MHz)
VCORNGE
CURRENT
VGA
640
480
60
31.5
25.175
00
101
72
37.7
31.500
00
101
75
37.5
31.500
00
101
85
43.3
36.000
00
110
SVGA
800
600
56
35.1
36.000
00
101
60
37.9
40.000
00
110
72
48.1
50.000
01
101
75
46.9
49.500
01
101
85
53.7
56.250
01
101
XGA
1024
768
60
48.4
65.000
01
101
70
56.5
75.000
01
110
75
60.0
78.750
01
110
80
64.0
85.500
10
101
85
68.3
94.500
10
101
SXGA
1280
1024
60
64.0
108.000
10
101
75
80.0
135.000
11
110
REV. A
AD9882
17
The COAST function allows the PLL to continue to run at the
same frequency, in the absence of the incoming Hsync signal or
during disturbances in Hsync (such as equalization pulses). This
may be used during the vertical sync period, or any other time
that the Hsync signal is unavailable. Also, the polarity of the
Hsync signal may be set through the Hsync Polarity Bit (Register
10H, Bit 6). If not using automatic polarity detection, the Hsync
polarity bit should be set to match the polarity of the Hsync
input signal.
TIMING (ANALOG INTERFACE)
The following timing diagrams show the operation of the AD9882.
The Output Data Clock signal is created so that its rising edge
always occurs between data transitions and can be used to latch
the output data externally.
DATA
HSOUT
t
SKEW
DATACK
t
DCYCLE
t
PER
Figure 7. Output Timing
Hsync Timing
Horizontal Sync (Hsync) is processed in the AD9882 to elimi-
nate ambiguity in the timing of the leading edge with respect to
the phase-delayed pixel clock and data.
The Hsync input is used as a reference to generate the pixel
sampling clock. The sampling phase can be adjusted, with respect
to Hsync, through a full 360
in 32 steps via the Phase Adjust
Register (Register 04H) to optimize the pixel sampling time.
Display systems use Hsync to align memory and display write
cycles, so it is important to have a stable timing relationship
between Hsync output (HSOUT) and data clock (DATACK).
Three things happen to Horizontal Sync in the AD9882. First,
the polarity of Hsync input is determined and will thus have a
known output polarity. The known output polarity can be pro-
grammed either active high or active low (Register 10H, Bit 5).
Second, HSOUT is aligned with DATACK and data outputs.
Third, the duration of HSOUT (in pixel clocks) is set via
Register 07H. HSOUT is the sync signal that should be used to
drive the rest of the display system.
Coast Timing
In most computer systems, the Hsync signal is provided continu-
ously on a dedicated wire. In these systems, the COAST function
is unnecessary and should be disabled using Register 11H, Bits 13.
In some systems, however, Hsync is disturbed during the Vertical
Sync period (Vsync). In other cases, Hsync pulses disappear.
In other systems, such as those that employ Composite Sync
(Csync) signals or embedded Sync-on-Green (SOG), Hsync
includes equalization pulses or other distortions during Vsync. To
avoid upsetting the clock generator during Vsync, it is important
to ignore these distortions. If the pixel clock PLL sees extraneous
pulses, it will attempt to lock to this new frequency and will
have changed frequency by the end of the Vsync period. It will
then take a few lines of correct Hsync timing to recover at the
beginning of a new frame, resulting in a "tearing" of the image
at the top of the display.
The COAST function is provided to eliminate this problem. It
is an internally generated signal, created by the sync processing
engine that disables the PLL input and allows the clock to free-run
at its then-current frequency. The PLL can free-run for several
lines without significant frequency drift.
REV. A
18
AD9882
TIMING DIAGRAMS
RGBIN
HSYNC
PXCK
HS
ADCCK
DATACK
DATAOUT
HSOUT
D0
D1
D2
D3
D4
D5
D6
D7
P0
P1
P2
P3
P4
P5
P6
P7
5 PIPE DELAY
VARIABLE DURATION
Figure 8. 4:4:4 Mode (for RGB and YPbPr)
RGBIN
P0
P1
P2
P3
P4
P5
P6
P7
HSYNC
PXCK
GOUTA
HS
ADCCK
DATACK
Y0
Y1
Y2
Y3
Y4
Y5
Y6
Y7
ROUTA
HSOUT
Pb0
Pr0
Pb2
Pr2
Pb4
Pr4
Pb6
Pr6
5 PIPE DELAY
VARIABLE DURATION
Figure 9. 4:2:2 Mode (for YPbPr Only)
REV. A
AD9882
19
Table VIII. Digital Interface Pin List
Pin Type
Mnemonic
Function
Value
Pin Number
Digital Video
R
X0+
Digital Input Channel 0 True
33
Data Inputs
R
X0
Digital Input Channel 0 Complement
32
R
X1+
Digital Input Channel 1 True
36
R
X1
Digital Input Channel 1 Complement
35
R
X2+
Digital Input Channel 2 True
39
R
X2
Digital Input Channel 2 Complement
38
Digital Video
R
XC+
Digital Data Clock True
41
Clock Inputs
R
XC
Digital Data Clock Complement
42
Termination
R
TERM
Control Pin for Setting the Internal Termination
28
Control
Resistance
Outputs
DE
Data Enable
3.3 V CMOS
86
HSOUT
Hsync Output
3.3 V CMOS
88
VSOUT
Vsync Output
3.3 V CMOS
87
CTL0, CTL1,
Decoded Control Bit Outputs
3.3 V CMOS
2225
CTL2, CTL3
HDCP
DDCSCL
HDCP Slave Serial Port Data Clock
3.3 V CMOS
53
DDCSDA
HDCP Slave Serial Port Data I/O
3.3 V CMOS
54
MCL
HDCP Master Serial Port Data Clock
3.3 V CMOS
81
MDA
HDCP Master Serial Port Data I/O
3.3 V CMOS
82
Power Supply
V
D
Main Power Supply
3.15 V to 3.45 V
PV
D
PLL Power Supply
3.15 V to 3.45 V
V
DD
Output Power Supply
2.2 V to 3.6 V
GND
Ground Supply
0 V
DIGITAL INTERFACE PIN DESCRIPTIONS
DIGITAL DATA INPUTS
R
X0+
Positive Differential Input Data (Channel 0)
R
X0
Negative Differential Input Data (Channel 0)
R
X1+
Positive Differential Input Data (Channel 1)
R
X1
Negative Differential Input Data (Channel 1)
R
X2+
Positive Differential Input Data (Channel 2)
R
X2
Negative Differential Input Data (Channel 2)
These six pins receive three pairs of differential, low voltage swing input pixel
data from a DVI transmitter.
DIGITAL CLOCK INPUTS
R
XC+
Positive Differential Input Clock
R
XC
Negative Differential Input Clock
These two pins receive the differential, low voltage swing input pixel clock from
a DVI transmitter.
TERMINATION CONTROL
R
TERM
Internal Termination Set Pin
This pin is used to set the termination resistance
for all of the digital interface high speed inputs.
To set, place a resistor of value equal to 10
the
desired input termination resistance between this
pin (Pin 28) and ground supply. Typically, the
value of this resistor should be 500
W.
OUTPUTS
DE
Data Enable Output
This pin outputs the state of data enable (DE).
The AD9882 decodes DE from the incoming
stream of data. The DE signal will be HIGH
during active video and will be LOW while there
is no active video.
DDCSCL
HDCP Slave Serial Port Data Clock
For use in communicating with the HDCP
enabled DVI transmitter.
DDCSDA
HDCP Slave Serial Port I/O
For use in communicating with the HDCP
enabled DVI transmitter.
MCL
HDCP Master Serial Port Data Clock
Connects to the EEPROM for reading the
encrypted HDCP keys.
MDA
HDCP Master Serial Port Data I/O
Connects to the EEPROM for reading the
encrypted HDCP keys.
CTL
Digital Control Outputs
These pins output the control signals for the
Red and Green channels. CTL0 and CTL1
correspond to the Red channel's input, while
CTL2 and CTL3 correspond to the Green
channel's input.
REV. A
20
AD9882
POWER SUPPLY
V
D
Main Power Supply
It should be as quiet as possible.
PV
D
PLL Power Supply
It should be as quiet as possible.
V
DD
Outputs Power Supply
The power for the data and clock outputs. It can
run at 3.3 V or 2.5 V.
GND
Ground
The ground return for all circuitry on the device.
It is recommended that the application circuit
board have a single, solid ground plane.
THEORY OF OPERATION (DIGITAL INTERFACE)
Capturing of the Encoded Data
The first step in recovering the encoded data is to capture the raw
data. To accomplish this, the AD9882 employs a high speed phase
locked loop (PLL) to generate clocks capable of oversampling
the data at the correct frequency. The data capture circuitry
continuously monitors the incoming data during horizontal and
vertical blanking times (when DE is low) and selects the best
sampling phase for each data channel independently. The phase
information is stored and used until the next blanking period
(one video line).
Data Frames
The digital interface data is captured in groups of 10 bits each,
which are called data frames. During the active data period,
each frame is made up of the nine encoded video data bits and
one dc balancing bit. The data capture block receives this
data serially but outputs each frame in parallel 10-bit words.
Special Characters
During periods of horizontal or vertical blanking time (when DE is
low), the digital transmitter will transmit special characters. The
AD9882 will receive these characters and use them to set the video
frame boundaries and the phase recovery loop for each chan-
nel. There are four special characters that can be received.
They are used to identify the top, bottom, left side, and right
side of each video frame. The data receiver can differentiate
these special characters from active data because the special
characters have a different number of transitions per data frame.
Channel Resynchronization
The purpose of the channel resynchronization block is to
resynchronize the three data channels to a single internal data
clock. Coming into this block, all three data channels can be on
different phases of the 3
oversampling PLL clock (0, 120,
and 240
). This block can resynchronize the channels from a
worst-case skew of one full input period (8.93 ns at 112 MHz).
Data Decoder
The data decoder receives frames of data and sync signals from
the data capture block (in 10-bit parallel words) and decodes
them into groups of eight RGB bits, two control bits, and a data
enable bit (DE).
HDCP
The AD9882 contains all the circuitry necessary for decryption
of a high bandwidth digital content protection encoded DVI
video stream. A typical HDCP implementation is shown in
Figure 10. Several features of the AD9882 make this possible
and add functionality to ease the implementation of HDCP.
The basic components of HDCP are included in the AD9882.
A slave serial bus connects to the DDC clock and DDC data
pins on the DVI connector to allow the HDCP enabled DVI
transmitter to coordinate the HDCP algorithm with the AD9882.
A second serial port (MDA/MCL) allows the AD9882 to read
the HDCP keys and key selection vector (KSV) stored in an
external serial EEPROM. When transmitting encrypted video,
the DVI transmitter enables HDCP through the DDC port.
The AD9882 then decodes the DVI stream using information
provided by the transmitter, HDCP keys, and KSV.
The AD9882 allows the MDA and MCL pins to be three-stated
using the MDA/MCL three-state bit (Register 1B, Bit 7) in the
configuration registers. The three-state feature allows the EEPROM
to be programmed in-circuit. The MDA/MCL port must be
three-stated before attempting to program the EEPROM using
an external master. The keys will be stored in an I
2
C compatible
3.3 V serial EEPROM of at least 512 bytes in size. The EEPROM
should have a device address of A0H.
Proprietary software licensed from Analog Devices encrypts
the keys and creates properly formatted EEPROM images for
use in a production environment. Encrypting the keys helps
maintain the confidentiality of the HDCP keys as required by
the HDCP v1.0 specification. The AD9882 includes hard-
ware for decrypting the keys in the external EEPROM.
ADI will provide a royalty free license for the proprietary
software needed by customers to encrypt the keys between
the AD9882 and the EEPROM only after customers provide
evidence of a completed HDCP Adopter's license agreement
and sign ADI's software license agreement. The Adopter's
license agreement is maintained by Digital Content Protection,
LLC, and can be downloaded from www.digital-cp.com.
To obtain ADI's software license agreement, contact the Display
Electronics Product Line directly by sending an email to
flatpanel_apps@analog.com.
DDC CLOCK
DDC DATA
DVI
CONNECTOR
SCL
SDA
EEPROM
3.3V
5k PULL-UP
RESISTORS
3.3V
5k PULL-UP
RESISTORS
150 SERIES
RESISTORS
DDC SCL
DDC SDA
AD9882
MCL
MDA
3.3V
S
D
Figure 10. HDCP Implementation Using the AD9882
REV. A
AD9882
21
GENERAL TIMING DIAGRAMS (DIGITAL INTERFACE)
80%
20%
D
LHT
80%
20%
D
HLT
Figure 11. Digital Output Rise and Fall Times
T
CIH
, R
CIH
T
CIP
, R
CIP
T
CIL
, R
CIL
Figure 12. Clock Cycle/High/Low Times
T
CSS
V
DIFF
=
0V
V
DIFF
=
0V
RX0
RX1
RX2
Figure 13. Channel-to-Channel Skew Timing
TIMING MODE DIAGRAMS (DIGITAL INTERFACE)
TST
INTERNAL
FIRST PIXEL
SECOND PIXEL
THIRD PIXEL
FOURTH PIXEL
ODCLK
DATACK
DE
DATAOUT
Figure 14. DVI CLK Invert = 1 (Register 14, Bit 4)
TST
INTERNAL
FIRST PIXEL
SECOND PIXEL
THIRD PIXEL
FOURTH PIXEL
ODCLK
DATACK
DE
DATAOUT
Figure 15. DVI CLK Invert = 0 (Register 14, Bit 4)
REV. A
22
AD9882
2-WIRE SERIAL REGISTER MAP
The AD9882 is initialized and controlled by a set of registers that determines the operating modes. An external controller is employed
to write and read the Control Registers through the 2-wire serial interface port.
Table IX. Control Register Map
Hex
Read and Write
Default
Address
or Read Only
Bit
Value
Register Name
Function
00
RO
70
Chip Revisions
An 8-bit register that represents the silicon
level. Revision 0 = 0000 0000
01
R/W
70
0110 1001
PLL Div MSB
This register is for Bits [11:4] of the PLL
divider. Larger values mean the PLL operates
at a faster rate. This register should be loaded
first whenever a change is needed. (This will
give the PLL more time to lock.)
1
02
R/W
74
1101
****
PLL Div LSB
Bits [3:0] LSBs of the PLL divider word. Links
to PLL MSB to make a 12-bit register.
1
03
R/W
76
01
** ****
VCO Range
Selects VCO frequency range.
53
**00 1***
Charge Pump
Varies the current that drives the PLL loop filter.
04
R/W
73
1000 0
***
Phase Adjust
ADC clock phase adjustment. Larger values
mean more delay (1 LSB = T/32).
05
R/W
70
0000 1000
Clamp Placement
Places the clamp signal an integer number of
clock periods after the trailing edge of Hsync.
06
R/W
70
0001 0100
Clamp Duration
Number of clock periods that the clamp signal
is actively clamping.
07
R/W
70
0010 0000
Hsync Output Pulsewidth
Sets the number of pixel clocks that HSOUT
will remain active.
08
R/W
70
1000 0000
Red Gain
Controls the ADC input range (contrast) of the
red channel. Larger values give less contrast.
09
R/W
70
1000 0000
Green Gain
Controls the ADC input range (contrast) of the
green channel. Larger values give less contrast.
0A
R/W
70
1000 0000
Blue Gain
Controls the ADC input range (contrast) of the
blue channel. Larger values give less contrast.
0B
R/W
71
1000 000
*
Red Offset
Controls the dc offset (brightness) of the red
channel. Larger values decrease brightness.
0C
R/W
71
1000 000
*
Green Offset
Controls the dc offset (brightness) of the green
channel. Larger values decrease brightness.
0D
R/W
71
1000 000
*
Blue Offset
Controls the dc offset (brightness) of the blue
channel. Larger values decrease brightness.
0E
R/W
70
0010 0000
Sync Separator Threshold
Sets how many pixel clocks to count before
toggling high or low. This should be set to
some number greater than the maximum
Hsync or equalization pulsewidth.
0F
R/W
73
0111 1
***
Sync-On-Green Threshold
Sets the voltage level of the Sync-on-Green
slicer's comparator.
2
**** *0**
Active Interface Override
0 = No override
1 = User overrides, interface set by 0FH, Bit 1
1
**** **0*
Active Interface Select
0 = Analog interface active
1 = Digital interface active
This interface is selected only if Register 0FH,
Bit 2 is set to 1, or if both interfaces are active.
NOTE
1
The AD9882 only updates the PLL divide ratio when the LSBs are written to Register 02H.
REV. A
AD9882
23
Table IX. Control Register Map (continued)
Hex
Read and Write
Default
Address
or Read Only
Bit
Value
Register Name
Function
10
R/W
7
0
*** ****
Hsync Polarity Override
0 = Polarity determined by chip
1 = Polarity set by 10H, Bit 6
6
*1** ****
Input Hsync Polarity
0 = Active low polarity
1 = Active high polarity
5
**0* ****
Output Hsync Polarity
0 = Active high sync signal
1 = Active low sync signal
4
***0 ****
Active Hsync Override
0 = No override
1 = User overrides, analog Hsync set by 10H, Bit 3
3
**** 0***
Active Hsync Select
0 = Analog Hsync from the Hsync input pin
1 = Analog Hsync from SOG
This bit is used if Register 10H, Bit 4 is set to
1 or if both syncs are active.
2
**** *0**
Output Vsync Polarity
0 = Invert
1 = Not inverted
1
**** **0*
Active Vsync Override
0 = No override
1 = User overrides, analog Vsync set by 10H, Bit 0
0
**** ***0
Active Vsync Select
0 = Analog Vsync from the Vsync input pin
1 = Analog Vsync from sync separator
11
R/W
7
0
*** ****
Clamp Function
0 = Clamping with internal clamp
1 = Clamping disabled
6
*0** ****
Red Clamp Select
0 = Clamp to ground
1 = Clamp to midscale for red channel
5
**0* ****
Green Clamp Select
0 = Clamp to ground
1 = Clamp to midscale for green channel
4
***0 ****
Blue Clamp Select
0 = Clamp to ground
1 = Clamp to midscale for blue channel
3
**** 1***
Coast Select
0 = Disabled coast
1 = Coasting with internally generated coast signal
2
**** *0**
Coast Polarity Override
0 = Coast polarity determined by the chip
1 = Coast polarity set by 11H, Bit 1
This bit must be set to 1 to disable coast.
1
**** **1*
Input Coast Polarity
0 = Active low coast signal
1 = Active high coast signal
This bit must be set to 1 to disable coast.
12
R/W
70
0000 0000
Pre-Coast
Number of Hsync periods that coast goes active
prior to Vsync.
13
R/W
70
0000 0000
Post-Coast
Number of Hsync periods before coast goes inactive
following Vsync.
14
R/W
76
11
** ****
Output Drive Select
Selects among high, medium, and low output
drive strength.
5
**1* ****
Programmable Bandwidth
0 = Low bandwidth of 10 MHz
1 = High bandwidth of 300 MHz
4
***0 ****
DVI Clock Invert
0 = DVI data clock output not inverted
1 = DVI data clock output inverted
For digital interface only.
3
**** 0***
DVI PDO Three-State
0 = Normal outputs
1 = High impedance outputs
2
**** *0**
HDCP Address
Address Bit 0 = 0 for HDCP Slave Port
Address Bit 1 = 1 for HDCP Slave Port
1
**** **1*
Power-Down
0 = Full chip power-down
REV. A
24
AD9882
Table IX. Control Register Map (continued)
Hex
Read and Write
Default
Address
or Read Only
Bit
Value
Register Name
Function
14
R/W
0
**** ***0
Enable 4:2:2
0 = 4:4:4 mode
1 = 4:2:2 mode
15
RO
7
Analog Hsync Active
0 = Hsync not detected
1 = Hsync detected
6
Analog SOG Active
0 = Sync signal not detected on green channel
1 = Sync signal detected on green channel
5
Analog Vsync Active
0 = Vsync not detected
1 = Vsync detected
4
DVI Active
0 = Digital interface clock not detected
1 = Digital interface clock detected
3
Active Interface
0 = Analog interface active
1 = DVI interface active
16
RO
7
Active Hsync
0 = Hsync from the Hsync input pin
1 = Hsync from the SOG input
6
Hsync Polarity Detected
0 = Active low polarity detected
1 = Active high polarity detected
5
Active Vsync
0 = Vsync from the Vsync input pin
1 = Vsync from SOG
4
Vsync Polarity Detected
0 = Active high polarity detected
1 = Active low polarity detected
3
Coast Polarity Detected
0 = Active low polarity detected
1 = Active high polarity detected
This function works only with internal coast.
2
HDCP Keys Detected
0 = Not detected
1 = Detected
17
R/W
70
0000 0000
Test Register
Must be set to 1000 0000 for proper operation.
18
R/W
70
0000 000X
Test Register
Must be set to 1100 000x for proper operation.
19
R/W
70
0000 010X
Test Register
Must be set to 0111 110x for proper operation.
1A
R/W
70
0011 1111
Test Register
Must be set to default for proper operation.
1B
R/W
7
1
*** ****
MDA and MCL
0 = MDA and MCL three-stated
1 = MDA and MCL not three-stated
60
*111 0000
Test Register
Must be set to
*110 0111 for proper operation.
1C
R/W
70
0000 1111
Test Register
Must be set to default for proper operation.
1D
RO
70
Test Register
Reserved for future use.
1E
RO
70
Test Register
Reserved for future use.
REV. A
AD9882
25
2-WIRE SERIAL CONTROL REGISTER DETAIL
CHIP IDENTIFICATION
00
70
Chip Revision
An 8-bit register that represents the silicon revision. Revision 0
= 0000 0000.
PLL DIVIDER CONTROL
01
70
PLL Divide Ratio MSBs
The eight most significant bits of the 12-bit PLL divide ratio
PLLDIV. (The operational divide ratio is PLLDIV + 1.)
The PLL derives a pixel clock from the incoming Hsync signal.
The pixel clock frequency is then divided by an integer value,
such that the output is phase-locked to Hsync. This PLLDIV
value determines the number of pixel times (pixels plus horizontal
blanking overhead) per line. This is typically 20% to 30% more
than the number of active pixels in the display.
The 12-bit value of the PLL divider supports divide ratios from
221 to 4095. The higher the value loaded in this register, the
higher the resulting clock frequency with respect to a fixed Hsync
frequency.
VESA has established some standard timing specifications that will
assist in determining the value for PLLDIV as a function of the
horizontal and vertical display resolution and frame rate
(Table VII). However, many computer systems do not conform
precisely to the recommendations, and these numbers should be
used only as a guide. The display system manufacturer should
provide automatic or manual means for optimizing PLLDIV.
An incorrectly set PLLDIV will usually produce one or more
vertical noise bars on the display. The greater the error, the
greater the number of bars produced.
The power-up default value of PLLDIV is 1693 (PLLDIVM =
69H, PLLDIVL = DxH).
The AD9882 updates the full divide ratio only when the LSBs are
changed. Writing to this register by itself will not trigger an update.
02
74
PLL Divide Ratio LSBs
The four least significant bits of the 12-bit PLL divide ratio
PLLDIV. The operational divide ratio is PLLDIV + 1.
The power-up default value of PLLDIV is 1693 (PLLDIVM =
69H, PLLDIVL = DxH).
The AD9882 updates the full divide ratio only when this register
is written.
03
76
VCO Range Select
Two bits that establish the operating range of the clock generator.
VCORNGE must be set to correspond with the desired operating
frequency (incoming pixel rate).
The PLL VCO gives the best jitter performance while operating
at high frequencies. For this reason, in order to output low pixel
rates and still get good jitter performance, the PLL VCO actually
operates at a higher frequency but then divides down the clock
rate afterward. Table X shows the pixel rates for each VCO range
setting. The PLL output divisor is automatically selected with
the VCO range setting.
Table X. VCO Ranges
VCORNGE
Pixel Rate Range
00
1241
01
4182
10
82140
The power-up default value is VCORNGE = 01.
03
53
CURRENT
Charge Pump Current
Three bits that establish the current driving the loop filter in the
clock generator.
Table XI. Charge Pump Currents
Charge Pump
Current (
mA)
000
50
001
100
010
150
011
250
100
350
101
500
110
750
111
1500
CHARGE PUMP must be set to correspond with the desired
operating frequency (incoming pixel rate). See Table XI for the
charge pump current for each register setting.
The power-up default value is CURRENT = 001.
04
73
Phase Adjust
A 5-bit value that adjusts the sampling phase in 32 steps
across one pixel time. Each step represents an 11.25
shift in
sampling phase.
The power-up default Phase adjust value is 10H.
CLAMP TIMING
05
70
Clamp Placement
An 8-bit register that sets the position of the internally gener-
ated clamp.
When CLAMP FUNCTION (Register 11H, Bit 7) = 0, a clamp
signal is generated internally at a position established by the
clamp placement and for a duration set by the clamp duration.
Clamping is started (Clamp Placement) an integral number of
pixel periods after the trailing edge of Hsync. The clamp place-
ment may be programmed to any value between 1 and 255.
The clamp should be placed during a time that the input signal
presents a stable black-level reference, usually the back porch
period between Hsync and the image.
When CLAMP FUNCTION = 1, this register is ignored.
06
70
Clamp Duration
An 8-bit register that sets the duration of the internally gener-
ated clamp.
For the best results, the clamp duration should be set to include
the majority of the black reference signal time that follows the
Hsync signal trailing edge. Insufficient clamping time can produce
brightness changes at the top of the screen and a slow recovery from
large changes in the Average Picture Level (APL) or brightness.
When CLAMP FUNCTION = 1, this register is ignored.
REV. A
26
AD9882
HSYNC OUTPUT PULSEWIDTH
07
70
Hsync Output Pulsewidth
An 8-bit register that sets the duration of the Hsync output pulse.
The leading edge of the Hsync output is triggered by the internally
generated, phase adjusted PLL feedback clock. The AD9882
then counts a number of pixel clocks equal to the value in this
register minus one. This triggers the trailing edge of the Hsync
output, which is also phase adjusted.
INPUT GAIN
08
70
REDGAIN
RED Gain
An 8-bit word that sets the gain of the RED channel. The AD9882
can accommodate input signals with a full-scale range of between
0.5 V and 1.0 V p-p. Setting REDGAIN to 255 corresponds to
an input range of 1.0 V. A REDGAIN of 0 establishes an input
range of 0.5 V. Note that INCREASING REDGAIN results in
the picture having LESS CONTRAST (the input signal uses
fewer of the available converter codes). See Figure 2.
09
70
GREENGAIN GREEN Gain
An 8-bit word that sets the gain of the GREEN channel. See
REDGAIN (08).
0A
70
BLUEGAIN
BLUE Gain
An 8-bit word that sets the gain of the BLUE channel. See
REDGAIN (08).
INPUT OFFSET
0B
71
RED Channel Offset Adjust
A 7-bit offset binary word that sets the dc offset of the RED
channel. One LSB of offset adjustment equals approximately one
LSB change in the ADC offset. Therefore, the absolute magni-
tude of the offset adjustment scales as the gain of the channel is
changed. A nominal setting of 64 results in the channel nominally
clamping the back porch (during the clamping interval) to code 00.
An offset setting of 127 results in the channel clamping to code
63 of the ADC. An offset setting of 0 clamps to code 64 (off the
bottom of the range). Increasing the value of RED offset
DECREASES the brightness of the channel.
0C
71
GREEN Channel Offset Adjust
A 7-bit offset binary word that sets the dc offset of the GREEN
channel. See REDOFST (0B).
0D
71
BLUE Channel Offset Adjust
A 7-bit offset binary word that sets the dc offset of the BLUE
channel. See REDOFST (0B).
0E
70
Sync Separator Threshold
This register is used to set the responsiveness of the sync separator.
It sets how many internal 5 MHz clock periods the sync separa-
tor must count to before toggling high or low. It works like a
low-pass filter to ignore Hsync pulses in order to extract the
Vsync signal. This register should be set to some number greater
than the maximum Hsync pulsewidth. Note: the sync separator
threshold uses an internal dedicated clock with a frequency of
approximately 5 MHz.
The default for this register is 20H.
0F
73
Sync-on-Green Slicer Threshold
This register allows the comparator threshold of the Sync-on-Green
slicer to be adjusted. This register adjusts it in steps of 10 mV,
with the minimum setting equaling 10 mV and the maximum
setting equaling 330 mV.
The default setting is 15 decimal and corresponds to a threshold
value of 170 mV.
0F
2
AIO
Active Interface Override
This bit is used to override the automatic interface selection
(Bit 3 in Register 15H). To override, set this bit to logic 1. When
overriding, the active interface is set via Bit 1 in this register.
Table XII. Active Interface Override Settings
AIO
Result
0
Autodetermine the active interface.
1
Override, Bit 1 determines the active interface.
The default for this register is 0.
0F
1
AIS
Active Interface Select
This bit is used under two conditions. It is used to select the active
interface when the override bit is set (Register 0FH, Bit 2).
Alternatively, it is used to determine the active interface when
not overriding but both interfaces are detected.
Table XIII. Active Interface Select Settings
AIS
Result
0
Analog interface
1
Digital interface
The default for this register is 0.
10
7
Hsync Input Polarity Override
This register is used to override the internal circuitry that determines
the polarity of the Hsync signal going into the PLL.
Table XIV. Hsync Input Polarity Override Settings
Override Bit
Result
0
Hsync polarity determined by chip.
1
Hsync polarity determined by Register 10H,
Bit 6.
The default for Hsync polarity override is 0. (Polarity determined by chip.)
10
6
HSPOL
Hsync Input Polarity
A bit that must be set to indicate the polarity of the Hsync signal
that is applied to the PLL Hsync input.
Table XV. Hsync Input Polarity Settings
HSPOL
Function
0
Active LOW
1
Active HIGH
Active LOW means the leading edge of the Hsync pulse is negative-
going. All timing is based on the leading edge of Hsync, which
is the FALLING edge. The rising edge has no effect.
REV. A
AD9882
27
Active HIGH means the leading edge of the Hsync pulse is
positive-going. This means that timing will be based on the
leading edge of Hsync, which is now the RISING edge.
The device will operate if this bit is set incorrectly, but the inter-
nally generated clamp position, as established by Clamp Placement
(Register 05H), will not be placed as expected, which may
generate clamping errors.
The power-up default value is HSPOL = 1.
10
5
Hsync Output Polarity
One bit that determines the polarity of the Hsync output and the
SOG output. Table XVI shows the effect of this option. SYNC
indicates the logic state of the sync pulse.
Table XVI. Hsync Output Polarity Settings
Setting
SYNC
0
Logic 1 (positive polarity)
1
Logic 0 (negative polarity)
The default setting for this register is 0.
10
4
Active Hsync Override
This bit is used to override the automatic Hsync selection. To
override, set this bit to logic 1. When overriding, the active
Hsync is set via Bit 3 in this register.
Table XVII. Active Hsync Override Settings
Override
Result
0
Autodetermine the active Hsync.
1
Override. Bit 3 determines the active Hsync.
The default for this register is 0.
10
3
Active Hsync Select
This bit is used under two conditions. It is used to select the active
Hsync when the override bit is set (Bit 4). Alternately, it is used
to determine the active Hsync when not overriding, but both
Hsyncs are detected.
Table XVIII. Active Hsync Select Settings
Select
Result
0
Hsync input
1
Sync-on-Green input
The default for this register is 0.
10
2
Vsync Output Polarity
One bit that determines the polarity of the Vsync output.
Table XIX shows the effect of this option. SYNC indicates the
logic state of the sync pulse.
Table XIX. Vsync Output Polarity Settings
Setting
SYNC
1
Not invert
0
Invert
The default setting for this register is 0.
10
1
Active Vsync Override
This bit is used to override the automatic Vsync selection. To
override, set this bit to logic 1. When overriding, the active
interface is set via Bit 0 in this register.
Table XX. Active Vsync Override Settings
Override
Result
0
Autodetermine the active Vsync
1
Override. Bit 0 determines the active Vsync.
The default for this register is 0.
10
0
Active Vsync Select
This bit is used to select the active Vsync when the override bit
is set (Bit 1).
Table XXI. Active Vsync Select Settings
Select
Result
0
Vsync input
1
Sync separator output
The default for this register is 0.
11
7
Clamp Function
A bit that enables/disables clamping.
Table XXII. Clamp Input Signal Source Settings
Clamp Function
Function
0
Internally generated clamp enabled
1
Clamping disabled
A 0 enables the clamp timing circuitry controlled by clamp
placement and clamp duration. The clamp position and duration
is counted from the trailing edge of Hsync.
A 1 disables clamping. The three channels are clamped when
the CLAMP signal is active.
Power-up default value is CLAMP FUNCTION = 0.
11
6
RED Clamp Select
A bit that determines whether the RED channel is clamped to
ground or to midscale. For RGB video, all three channels are
referenced to ground. For YPbPr, the Y channel is referenced
to ground, but the PbPr channels are referenced to midscale.
Clamping to midscale actually clamps to Pin 74.
Table XXIII. RED Clamp Select Settings
Clamp
Function
0
Clamp to ground
1
Clamp to midscale (Pin 74)
The default setting for this register is 0.
REV. A
28
AD9882
11
5
GREEN Clamp Select
A bit that determines whether the GREEN channel is clamped
to ground or to midscale.
Table XXIV. GREEN Clamp Select Settings
Clamp
Function
0
Clamp to ground
1
Clamp to midscale (Pin 74)
The default setting for this register is 0.
11
4
BLUE Clamp Select
A bit that determines whether the BLUE channel is clamped to
ground or to midscale.
Table XXV. BLUE Clamp Select Settings
Clamp
Function
0
Clamp to ground
1
Clamp to midscale (Pin 74)
The default setting for this register is 0.
11
3
Coast Select
This bit is used to enable or disable the coast signal. If coast is
enabled, the additional decision of using the Vsync input pin or
the output from the sync separator needs to be made (Register
10H, Bits 1, 0). To disable coast, the user must set Register 11H,
Bit 2 to 1 and 11H, Bit 1 to 1.
Table XXVI. Coast Enable Settings
Select
Result
0
Coast disabled
1
Internally generated coast signal
The default for this register is 1.
11
2
Coast Input Polarity Override
This register is used to override the internal circuitry that deter-
mines the polarity of the coast signal going into the PLL. When
disabling coast, Register 11, Bit 2 must be set to 1 and Register
11H, Bit 1 must be set to 1. This register only works when Coast
is disabled. It does not work with internal Coast.
Table XXVII. Coast Input Polarity Override Settings
Override Bit
Result
0
Coast polarity determined by chip
1
Coast polarity determined by user
The default for coast polarity override is 0.
11
1
Coast Input Polarity
A bit to indicate the polarity of the coast signal that is applied to
the PLL coast input.
This register can only be used when coast is disabled and
Register 11H, Bit 2 is set to 1.
Table XXVIII. Coast Input Polarity Settings
CSTPOL
Function
0
Active LOW
1
Active HIGH
The power-up default value is CSTPOL = 1.
12
70
Pre-Coast
This register allows the coast signal to be applied prior to the
Vsync signal. This is necessary in cases where pre-equalization
pulses are present. This register defines the number of edges
that will be filtered before Vsync on a composite sync.
The default is 0.
13
70
Post-Coast
This register allows the coast signal to be applied following the
Vsync signal. This is necessary in cases where post-equalization
pulses are present. The step size for this control is one Hsync
period. This register defines the number of edges that will be
filtered after Vsync on a composite sync.
The default is 0.
14
76
Output Drive
The two bits select the drive strength for the high speed digital
outputs (all data output and clock output pins). Higher drive
strength results in faster rise/fall times, and in general makes it
easier to capture data. Lower drive strength results in slower
rise/fall times and helps reduce EMI and digitally generated
power supply noise.
Table XXIX. Output Drive Strength Settings
Bit 7
Bit 6
Result
1
X
High drive strength
0
1
Medium drive strength
0
0
Low drive strength
The default for this register is 11, high drive strength. (This option works on
both the analog and digital interfaces.)
14
5
Programmable Analog Bandwidth
Bits that select the analog bandwidth.
Table XXX. Analog Bandwidth Control
Bit 5
Analog Bandwidth
0
10 MHz
1
300 MHz
14
4
Clk Inv
Data Output Clock Invert
A control bit for the inversion of the output data clock (Pin 85).
This function works only for the digital interface. When not
inverted, data is output on the falling edge of the data clock.
See the timing diagrams, Figures 14 and 15, to see how this
affects timing.
Table XXXI. Clock Output Invert Settings
Clk Inv
Function
0
Not inverted
1
Inverted
The default for this register is 0 (not inverted).
REV. A
AD9882
29
14
3
PDO
Power-Down Outputs
A bit that can put the outputs in a high impedance mode. This
applies to the 24 data output pins, HSOUT, VSOUT, and DE Pins.
Table XXXII. Power-Down Output Settings
PDO
Function
0
Normal operation
1
Three-state
The default for this register is 0. (This option works on both the analog and
digital interfaces.)
14
2
HDCP Address
This bit is used to set the HDCP Slave Port address.
Table XXXIII. HDCP Address Settings
Address Bit
Result
0
0 for HDCP Slave Port
1
1 for HDCP Slave Port
The default for this register is 0.
14
1
PWRDN
This bit is used to control chip power-down. See the section on
power management for details about which blocks are actually
powered down.
Table XXXIV. Power-Down Settings
Select
Result
0
Power-down
1
Normal operation
The default for this register is 1.
14
0
4:2:2 Output Mode Select
A bit that configures the output data in 4:2:2 mode. This mode
can be used to reduce the number of data lines used from 24
to 16 for applications using YPbPr graphics signals. A timing
diagram for this mode is shown in Figure 9. Recommended
input and output configurations are shown in Table XXXVI.
In 4:2:2 mode, the RED and BLUE channels can be interchanged
to help satisfy board layout or timing requirements, but the
GREEN channel must be configured for Y.
Table XXXV. 4:2:2 Output Mode Select
Select
Output Mode
0
4:4:4
1
4:2:2
Table XXXVI. 4:2:2 Input/Output Configuration
Channel
Input Connection
Output Format
RED
Pr
Pb/Pr
GREEN
Y
Y
BLUE
Pr
High impedance
15
7
Hsync Detect
This bit is used to indicate when activity is detected on the
Hsync input pin (Pin 79). If Hsync is held high or low, activity
will not be detected.
Table XXXVII. Hsync Detection Results
Detect
Function
0
No activity detected
1
Activity detected
The Sync Processing Block Diagram, Figure 18, shows where this function is
implemented.
15
6
Sync-on-Green Detect
This bit is used to indicate when sync activity is detected on the
Sync-on-Green input pin (Pin 64).
Table XXXVIII. Sync-on-Green Detection Results
Detect
Function
0
No activity detected
1
Activity detected
The Sync Processing Block Diagram, Figure 18, shows where this function is
implemented.
Note: If no Sync signal is presented on the GREEN video input,
normal video may still trigger activity.
15
5
Vsync Detect
This bit is used to indicate when activity is detected on the
Vsync input pin (Pin 80). If Vsync is held high or low, activity
will not be detected.
Table XXXIX. Vsync Detection Results
Detect
Function
0
No activity detected
1
Activity detected
The Sync Processing Block Diagram, Figure 18, shows where this function is
implemented.
15
4
Digital Interface Clock Detect
This bit is used to indicate when activity is detected on the
digital interface clock input.
Table XL. Digital Interface Clock Detection Results
Detect
Function
0
No activity detected
1
Activity detected
The Sync Processing Block Diagram, Figure 18, shows where this function is
implemented.
REV. A
30
AD9882
15
3
Active Interface
This bit is used to indicate which interface should be active, analog
or digital. It checks for activity on the analog interface and for
activity on the digital interface, then determines which should be
active according to Table XLI. Specifically, analog interface detec-
tion is determined by OR-ing Bits 7, 6, and 5 in this register. Digital
interface detection is determined by Bit 4 in this register. If both
interfaces are detected, the user can determine which has priority
via Bit 1 in Register 0FH. The user can override this function
via Bit 2 in Register 0FH. If the override bit is set to logic 1, then
this bit will be forced to the same state as Bit 1 in Register 0FH.
Table XLI. Active Interface Results
Bits 7, 6, or 5
Bit 4
(Analog
(Digital
Detection)
Detection)
Override
AI
0
0
0
Soft
Power-Down
(Seek Mode)
0
1
0
1
1
0
0
0
1
1
0
Bit 1 in 0FH
X
X
1
Bit 1 in 0FH
AI = 0 means analog interface
AI = 1 means digital interface
The override bit is in Register 0FH, Bit 2.
16
7
AHS
Active Hsync
This bit indicates which Hsync input source is being used by the
PLL (Hsync input or Sync-on-Green). Bits 6 and 7 in Register
15H determine which source is used. If both Hsync and SOG
are detected, the user can determine which has priority via Bit 3
in Register 10H. The user can override this function via Bit 4
in Register 10H. If the override bit is set to logic 1, then this
bit will be forced to the same state as Bit 3 in Register 10H.
Table XLII. Active Hsync Results
Hsync Detect SOG Detect
Override
AHS
Register 15H
Register 15H Register 10H
Register 16H
Bit 7
Bit 6
Bit 4
Bit 7
0
0
0
Bit 3 in 10H
0
1
0
1
1
0
0
0
1
1
0
Bit 3 in 10H
X
X
1
Bit 3 in 10H
AHS = 0 means use the Hsync pin input for Hsync
AHS = 1 means use the SOG pin input for Hsync
The override bit is in Register 10H, Bit 4.
16
6
Detected Hsync Input Polarity Status
This bit reports the status of the Hsync input polarity detection
circuit. It can be used to determine the polarity of the Hsync
input. The detection circuit's location is shown in the Sync
Processing Block Diagram, Figure 18.
Table XLIII. Detected Hsync Input Polarity Status
Hsync Polarity
Status
Result
0
Hsync polarity is negative/active low.
1
Hsync polarity is positive/active high.
16
5
AVS
Active Vsync
This bit indicates which Vsync source is being used for the analog
interface: the Vsync input or output from the sync separator.
If the override bit (10H, Bit 1) is set to logic 1, then this bit will be
forced to the same state as Bit 0 in Register 10H.
Table XLIV. Active Vsync Results
Vsync Detect
Override
Register 16H
Register 10H
Bit 5
Bit 1
AVS
0
0
0
1
0
1
X
1
Bit 0 in 10H
AVS = 0 means Vsync input
AVS = 1 means Sync separator
The override bit is in Register 10H, Bit 1.
16
4
Detected Vsync Output Polarity Status
This bit reports the status of the Vsync output polarity detection
circuit. It can be used to determine the polarity of the Vsync
output. The detection circuit's location is shown in the Sync
Processing Block Diagram, Figure 18.
Table XLV. Detected Vsync Input Polarity Status
Vsync Polarity Status
Result
0
Vsync polarity is active high.
1
Vsync polarity is active low.
16
3
Detected Coast Polarity Status
This bit reports the status of the coast input polarity detection
circuit. The detection circuit's location is shown in the Sync
Processing Block Diagram, Figure 18. This bit only applies to
the internal Coast and does not apply when Coast is disabled.
Table XLVI. Detected Coast Input Polarity Status
Hsync Polarity
Status
Result
0
Coast polarity is negative/active low.
1
Coast polarity is positive/active high.
16
2
Key Read Verification
This bit reports wherever HDCP keys are detected.
Table XLVII. Key Read Verification
Detect
Function
0
Not detected
1
Detected
1B
7
MDA and MCL Three-State
The MDA and MCL three-state feature allows the EEPROM to
be programmed in-circuit. The MDA/MCL port must be three-
stated before attempting to program the EEPROM using an
external master. The keys will be stored in an I
2
C compatible
3.3 V serial EEPROM of at least 512 bytes. The EEPROM
should have a device address of A0H.
REV. A
AD9882
31
2-WIRE SERIAL CONTROL PORT
A 2-wire serial control interface is provided. Two AD9882
devices may be connected to the 2-wire serial interface, with each
device having a unique address.
The 2-wire serial interface comprises a clock (SCL) and a
bidirectional data (SDA) pin. The analog flat panel interface
acts as a slave for receiving and transmitting data over the serial
interface. When the serial interface is not active, the logic levels
on SCL and SDA are pulled HIGH by external pull-up resistors.
Data received or transmitted on the SDA line must be stable for
the duration of the positive-going SCL pulse. Data on SDA must
change only when SCL is LOW. If SDA changes state while SCL
is HIGH, the serial interface interprets that action as a start or
stop sequence.
There are five components to serial bus operation:
Start signal
Slave address byte
Base register address byte
Data byte to read or write
Stop signal
When the serial interface is inactive (SCL and SDA are HIGH),
communications are initiated by sending a start signal. The start
signal is a HIGH-to-LOW transition on SDA while SCL is HIGH.
This signal alerts all slaved devices that a data transfer sequence
is coming.
The first eight bits of data transferred after a start signal com-
prise a 7-bit slave address (the first seven bits) and a single
R/
W bit (the eighth bit). The R/W bit indicates the direction of
data transfer: read from (1) or write to (0) the slave device. If the
transmitted slave address matches the address of the device (set
by the state of the SA input pin in Table XLVIII), the AD9882
acknowledges by bringing SDA LOW on the ninth SCL pulse.
If the addresses do not match, the AD9882 does not acknowledge.
Table XLVIII. Serial Port Addresses
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
A6
A5
A4
A3
A2
A1
A0
(MSB)
(LSB)
1
0
0
1
1
0
0
1
0
0
1
1
0
1
Data Transfer via Serial Interface
For each byte of data read or written, the MSB is the first bit of
the sequence.
If the AD9882 does not acknowledge the master device during a
write sequence, the SDA remains HIGH so the master can gener-
ate a stop signal. If the master device does not acknowledge the
AD9882 during a read sequence, the AD9882 interprets this
as "end of data." The SDA remains HIGH so the master can
generate a stop signal.
Writing data to specific control registers of the AD9882 requires
that the 8-bit address of the control register of interest be written
after the slave address has been established. This control regis-
ter address is the base address for subsequent write operations.
The base address autoincrements by one for each byte of data
written after the data byte intended for the base address. If there
are more bytes transferred than there are available addresses, the
address will not increment and will remain at its maximum value
of 1Eh. Any base address higher than 1Eh will not produce an
acknowledge signal.
Data are read from the control registers of the AD9882 in a
similar manner. Reading requires two data transfer operations:
The base address must be written with the R/
W bit of the slave
address byte LOW to set up a sequential read operation.
Reading (the R/
W bit of the slave address byte HIGH) begins at
the previously established base address. The address of the read
register autoincrements after each byte is transferred.
To terminate a read/write sequence to the AD9882, a stop signal
must be sent. A stop signal comprises a LOW-to-HIGH transition
of SDA while SCL is HIGH. The timing for the read/write is
shown in Figure 16, and a typical byte transfer is shown in
Figure 17.
A repeated start signal occurs when the master device driving the
serial interface generates a start signal without first generating a
stop signal to terminate the current communication. This is used
to change the mode of communication (read, write) between the
slave and master without releasing the serial interface lines.
t
BUFF
t
STAH
t
DHO
t
DAL
t
DAH
t
DSU
t
STASU
t
STOSU
SDA
SCL
Figure 16. Serial Port Read/Write Timing
REV. A
32
AD9882
Serial Interface Read/Write Examples
Write to one control register
Start signal
Slave address byte (R/W bit = LOW)
Base address byte
Data byte to base address
Stop signal
Write to four consecutive control registers
Start signal
Slave address byte (R/W bit = LOW)
Base address byte
Data byte to base address
Data byte to (base address + 1)
Data byte to (base address + 2)
Data byte to (base address + 3)
Stop signal
Read from one control register
Start signal
Slave address byte (R/W bit = LOW)
Base address byte
Start signal
Slave address byte (R/W bit = HIGH)
Data byte from base address
Stop signal
Read from four consecutive control registers
Start signal
Slave address byte (R/W bit = LOW)
Base address byte
Start signal
Slave address byte (R/W bit = HIGH)
Data byte from base address
Data byte from (base address + 1)
Data byte from (base address + 2)
Data byte from (base address + 3)
Stop signal
SDA
SCL
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
ACK
Figure 17. Serial Interface, Typical Byte Transfer
REV. A
AD9882
33
SOG
MUX 1
DVI
HSYNC IN
VSYNC IN
SYNC STRIPPER
ACTIVITY
DETECT
ACTIVITY
DETECT
1/S
INTEGRATOR
VSYNC
MUX 4
SOG
OUT
MUX 5
MUX 6
HSYNC
OUT
VSYNC
OUT
DE
CLOCK
GENERATOR
HSYNC OUT
PIXEL CLOCK
POLARITY
DETECT
COAST
POLARITY
DETECT
HSYNC
MUX 2
PLL
COMP
SYNC
SYNC SEPARATOR
MUX 3
HSYNC
VSYNC
DE
ACTIVITY
DETECT
NEGATIVE
PEAK
CLAMP
Figure 18. Sync Processing Block Diagram
Table XLIX. Control of the Sync Block Muxes via the Serial Register
Mux Number(s)
Serial Bus Control Bit
Control Bit State
Result
1 and 2
10H: Bit 3
0
Pass Hsync
1
Pass Sync-on-Green
3
10H: Bit 0
0
Pass Vsync
1
Pass Sync Separator Signal
4, 5, and 6
0FH: Bit 1
0
Pass Analog Interface Signals
1
Pass Digital Interface Signals
REV. A
34
AD9882
THEORY OF OPERATION
Sync Stripper
This section is devoted to the basic operation of the sync pro-
cessing engine. (Refer to Figure 18.)
The purpose of the sync stripper is to extract the sync signal from
the green graphics channel. A sync signal is not present on all
graphics systems; only those with Sync-on-Green. The sync signal
is extracted from the GREEN channel in a two-step process.
First, the SOG input is clamped to its negative peak (typically
0.3 V below the black level). Next, the signal goes to a comparator
with a variable trigger level, nominally 0.15 V above the clamped
level. The output signal is typically a composite sync signal
containing both Hsync and Vsync.
Sync Separator
A sync separator extracts the Vsync signal from a composite sync
signal. It does this through a low-pass filter-like or integrator-
like operation. It works on the idea that the Vsync signal stays
active for a much longer time than the Hsync signal. So, it rejects
any signal shorter than a threshold value, which is somewhere
between an Hsync pulsewidth and a Vsync pulsewidth.
The sync separator on the AD9882 is simply an 8-bit digital
counter with a 5 MHz clock. It works independently of the polarity
of the composite sync signal. (Polarities are determined elsewhere
on the chip.) The basic idea is that the counter counts up when
Hsync pulses are present. But since Hsync pulses are relatively
short in width, the counter only reaches a value of N before the
pulse ends. It then starts counting down, eventually reaching
0 before the next Hsync pulse arrives. The specific value of N will
vary for different video modes, but will always be less than 255.
For example, with a 1
ms width Hsync, the counter will only reach
5 (1
ms/200 ns = 5). Now, when Vsync is present on the composite
sync the counter will also count up. However, since the Vsync
signal is much longer, it will count to a higher number M. For
most video modes, M will be at least 255. So, Vsync can be detected
on the composite sync signal by detecting when the counter
counts to higher than N. The specific count that triggers detection
(T) can be programmed through the serial register (0EH).
Once Vsync has been detected, a similar process detects when
it goes inactive. At detection, the counter first resets to 0, then
starts counting up when Vsync goes away. In a way similar to
the previous case, it will detect the absence of Vsync when the
counter reaches the threshold count (T). In this way, it will
reject noise and/or serration pulses. Once Vsync is determined
to be absent, the counter resets to 0 and begins the cycle again.
PCB LAYOUT RECOMMENDATIONS
The AD9882 is a high precision, high speed analog device. In
order to derive the maximum performance out of the part, it is
important to have a well laid out board. The following is a guide
for designing a board using the AD9882.
Analog Interface Inputs
Using the following layout techniques on the graphics inputs is
extremely important.
Minimize the trace length running into the graphics inputs. This
is accomplished by placing the AD9882 as close as possible to the
graphics VGA connector. Long input trace lengths are undesirable
because they will pick up more noise from the board and other
external sources.
Place the 75
W termination resistors (see Figure 1) as close to the
AD9882 chip as possible. Any additional trace length between the
termination resistors and the input of the AD9882 increases the
magnitude of reflections, which will corrupt the graphics signal.
Use 75
W matched impedance traces. Trace impedances other
than 75
W will also increase the chance of reflections.
The AD9882 has a very high input bandwidth (300 MHz). While
this is desirable for acquiring a high resolution PC graphics signal
with fast edges, it means that it will also capture any high frequency
noise present. Therefore, it is important to reduce the amount
of noise that gets coupled to the inputs. Avoid running any
digital traces near the analog inputs.
Due to the high bandwidth of the AD9882, sometimes low-pass
filtering the analog inputs can help to reduce noise. (For many
applications, filtering is unnecessary.) Experiments have shown
that placing a series ferrite bead prior to the 75
W termination
resistor is helpful in filtering out excess noise. Specifically, the
part used was the #2508051217Z0 from Fair-Rite, but different
applications may work best with different bead values. Alternatively,
placing a 100
W to 120 W resistor between the 75 W termination
resistor and the input coupling capacitor can also be beneficial.
Digital Interface Inputs
Many of the same techniques that are recommended for the analog
interface inputs should also be used for the digital interface inputs.
It is important to minimize trace lengths, then make the input
trace impedances match the input termination (typically 50
W).
Each differential input pair (R
X0+
, R
X0
, R
XC+
, R
XC
, and so on)
should be routed together using 50
W strip line routing techniques
and should be kept as short as possible. No other components,
e.g., no clamping diodes, should be placed on these inputs. Every
effort should be made to route these signals on a single layer
(component layer) with no vias.
Power Supply Bypassing
Bypassing each power supply pin with a 0.1
mF capacitor is
recommended. The exception is the case in which two or more
supply pins are adjacent to each other. For these groupings of
powers/grounds, it is necessary to have one bypass capacitor.
The fundamental idea is to have a bypass capacitor within about
0.5 cm of each power pin. Also, avoid placing the capacitor on
the side of the PC board opposite the AD9882, as that interposes
resistive vias in the path.
The bypass capacitors should be physically located between the
power plane and the power pin. Current should flow from the
power plane
capacitor power pin. Do not make the power
connection between the capacitor and the power pin. Placing a
via underneath the capacitor pads, down to the power plane, is
generally the best approach.
It is particularly important to maintain low noise and good
stability of PV
D
(the clock generator supply). Abrupt changes
in PV
D
can result in similarly abrupt changes in sampling clock
phase and frequency. This can be avoided by careful attention to
regulation, filtering, and bypassing. It is highly desirable to pro-
vide separate regulated supplies for each of the analog circuitry
groups (V
D
and PV
D
).
REV. A
AD9882
35
Some graphic controllers use levels of power when active (during
active picture time) that are substantially different from those used
when they are idle (during horizontal and vertical sync periods).
This can result in a measurable change in the voltage supplied to
the analog supply regulator, which can in turn produce changes
in the regulated analog supply voltage. This can be mitigated by
regulating the analog supply, or at least PV
D
, from a different,
cleaner, power source (for example, from a 12 V supply).
Using a single ground plane for the entire board is also rec-
ommended. Experience has repeatedly shown that the noise
performance is the same or better with a single ground plane.
Using multiple ground planes can be detrimental because each
separate ground plane is smaller than one common ground
plane, and long ground loops can result.
In some cases, using separate ground planes is unavoidable. For
those cases where they must be used, it is recommended that at
least a single ground plane be placed under the AD9882. The loca-
tion of the split should be at the receiver of the digital outputs. For
this case, it is even more important to place components wisely
because the current loops will be much longer (current takes the
path of least resistance). The following is an example of a current
loop: power plane
AD9882 digital output trace digital
data receiver
digital ground plane analog ground plane.
PLL
Place the PLL loop filter components as close to the FILT pin
as possible.
Do not place any digital or other high frequency traces near
these components.
Use the values suggested in the data sheet with 10% or smaller
tolerances.
Outputs (Data and Clocks)
Try to minimize the trace length that the digital outputs have to
drive. Longer traces have higher capacitance and require more
current, which causes more internal digital noise.
Shorter traces reduce the possibility of reflections.
Adding a series resistor with a value of 22
W to 100 W can suppress
reflections, reduce EMI, and reduce the current spikes inside of
the AD9882. However, if 50
W traces are used on the PCB, the
data output should not need these resistors.
A 22
W resistor on the DATACK output should provide good
impedance matching that will reduce reflections. If EMI or
current spiking is a concern, use a lower drive strength setting
by adjusting register 14H. If series resistors are used, place them as
close to the AD9882 pins as possible (but avoid adding vias or
extra length to the output trace in order to get the resistors closer).
If possible, limit the capacitance that each of the digital outputs
drives to less than 10 pF. This can be accomplished easily by
keeping traces short and by connecting the outputs to only one
device. Loading the outputs with excessive capacitance will
increase the current transients inside the AD9882, creating
more digital noise on its power supplies.
Digital Inputs
The digital inputs on the AD9882 were designed to work
with 3.3 V signals, but are tolerant of 5.0 V signals. No extra
components need to be added if 5.0 V logic is used.
Any noise that gets onto the Hsync input trace will add jitter to
the system. Therefore, minimize the trace length and do not
run any digital or other high frequency traces near it.
Voltage Reference
Bypass with a 0.1
mF capacitor. Place as close to the AD9882
pin as possible. Make the ground connection as short as possible.
C0288901/03(A)
PRINTED IN U.S.A.
36
AD9882
REV. A
OUTLINE DIMENSIONS
100-Lead Quad Flatpack [LQFP]
(ST-100)
Dimensions shown in millimeters
TOP VIEW
(PINS DOWN)
1
25
26
51
50
75
76
100
14.00 BSC SQ
0.50 BSC
0.27
0.22
0.17
1.60 MAX
SEATING
PLANE
12
TYP
0.75
0.60
0.45
VIEW A
7
3.5
0
0.15
0.05
0.08
MAX LEAD
COPLANARITY
SEATING
PLANE
VIEW A
ROTATED 90 CCW
0.20
0.09
16.00 BSC SQ
COMPLIANT TO JEDEC STANDARDS MS-026BED
THE ACTUAL POSITION OF EACH LEAD IS WITHIN 0.08 OF ITS IDEAL
POSITION WHEN MEASURED IN THE LATERAL DIRECTION
12.00
REF
Revision History
Location
Page
1/03--Data Sheet changed from REV.
0 to REV. A.
Edits to PIN CONFIGURATION headings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Edits to Table IX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
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