1745i.pm6
1
LTC1745
1745i
Low Noise,12-Bit, 25Msps ADC
January 2003
s
Sample Rate: 25Msps
s
72.5dB SNR and 96dB SFDR (3.2V Range)
s
71dB SNR and 96dB SFDR (2V Range)
s
No Missing Codes
s
Single 5V Supply
s
Low Power Dissipation: 380mW
s
Selectable Input Ranges:
1V or
1.6V
s
240MHz Full Power Bandwidth S/H
s
Output Enable
s
Two's Complement or Offset Binary Outputs
s
Out-of-Range Indicator
s
Data Ready Output Clock
s
48-Pin TSSOP Package
s
50Msps Pin-for-Pin Upgrade (LTC1743)
s
14-Bit Plug Compatible Upgrade (LTC1746)
s
Telecommunications
s
Medical Imaging
s
Receivers
s
Cellular Base Stations
s
Spectrum Analysis
s
Imaging Systems
FEATURES
DESCRIPTIO
N
U
APPLICATIO S
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
BLOCK DIAGRA
W
The LTC
1745 is a 25Msps, sampling 12-bit A/D con-
verter designed for digitizing high frequency, wide dy-
namic range signals. Pin selectable input ranges of
1V
and
1.6V along with a resistor programmable mode
allow the LTC1745's input range to be optimized for a wide
variety of applications.
The LTC1745 is perfect for demanding communications
applications with AC performance that includes 72.5dB
SNR and 96dB spurious free dynamic range. Ultralow jitter
of 0.3ps
RMS
allows undersampling of IF frequencies of up
to 70MHz with excellent noise performance. DC specs
include
1LSB INL and
0.75LSB DNL over temperature.
The digital interface is compatible with 5V, 3V and 2V logic
systems. The ENC and ENC inputs may be driven differen-
tially from PECL, GTL and other low swing logic families or
from single-ended TTL or CMOS. The low noise, high gain
ENC and ENC inputs may also be driven by a sinusoidal
signal without degrading performance. A separate output
power supply can be operated from 0.5V to 5V, making it
easy to connect directly to any low voltage DSPs or FIFOs.
The TSSOP package with a flow-through pinout simplifies
the board layout.
Final Electrical Specifications
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
25Msps, 12-Bit ADC with a
1V Differential Input Range
12-BIT
PIPELINED ADC
12
S/H
AMP
1V
DIFFERENTIAL
ANALOG INPUT
A
IN
+
A
IN
SENSE
V
CM
4.7
F
DIFF AMP
REFLA
REFHB
GND
1745 BD
ENC
4.7
F
1
F
1
F
0.1
F
0.1
F
REFHA
REFLB
BUFFER
RANGE
SELECT
2.35V
REF
OUTPUT
LATCHES
CONTROL LOGIC
OV
DD
V
DD
OGND
0.5V TO 5V
5V
0.1
F
1
F
1
F
1
F
D11
D0
CLKOUT
OF
ENC
DIFFERENTIAL
ENCODE INPUT
OE
MSBINV
0.1
F
2
LTC1745
1745i
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Resolution (No Missing Codes)
q
12
Bits
Integral Linearity Error
(Note 6)
q
1
0.4
1
LSB
Differential Linearity Error
q
0.75
0.2
0.75
LSB
Offset Error
(Note 7)
q
30
5
30
mV
Gain Error
External Reference (SENSE = 1.6V)
q
2.5
1
2.5
%FS
Full-Scale Tempco
I
OUT(REF)
= 0
40
ppm/
C
ORDER PART
NUMBER
OV
DD
= V
DD
(Notes 1, 2)
Supply Voltage (V
DD
) ............................................. 5.5V
Analog Input Voltage (Note 3) .... 0.3V to (V
DD
+ 0.3V)
Digital Input Voltage (Note 4) ..... 0.3V to (V
DD
+ 0.3V)
Digital Output Voltage ................. 0.3V to (V
DD
+ 0.3V)
OGND Voltage ........................................... 0.3V to 0.3V
Power Dissipation ............................................ 2000mW
Operating Temperature Range
LTC1745C ............................................... 0
C to 70
C
LTC1745I ............................................ 40
C to 85
C
Storage Temperature Range ................. 65
C to 150
C
Lead Temperature (Soldering, 10 sec).................. 300
C
LTC1745CFW
LTC1745IFW
T
JMAX
= 150
C,
JA
= 35
C/W
The
q
indicates specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. (Note 5)
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
PACKAGE/ORDER I
N
FOR
M
ATIO
N
W
U
U
CO VERTER CHARACTERISTICS
U
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Analog Input Range (Note 8)
4.75V
V
DD
5.25V
q
1 to
1.6
V
I
IN
Analog Input Leakage Current
q
1
1
A
C
IN
Analog Input Capacitance
Sample Mode ENC < ENC
8
pF
Hold Mode ENC > ENC
4
pF
t
ACQ
Sample-and-Hold Acquisition Time
q
15
18
ns
t
AP
Sample-and-Hold Acquisition Delay Time
0
ns
t
JITTER
Sample-and-Hold Acquisition Delay Time Jitter
0.3
ps
RMS
CMRR
Analog Input Common Mode Rejection Ratio
1.0V < (A
IN
= A
IN
+
) < 3.5V
80
dB
The
q
indicates specifications which apply over the full operating temperature range, otherwise
specifications are at T
A
= 25
C. (Note 5)
A ALOG I PUT
U
U
Consult LTC Marketing for parts specified with wider operating temperature ranges.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
TOP VIEW
FW PACKAGE
48-LEAD PLASTIC TSSOP
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
SENSE
V
CM
GND
A
IN
+
A
IN
GND
V
DD
V
DD
GND
REFLB
REFHA
GND
GND
REFLA
REFHB
GND
V
DD
V
DD
GND
V
DD
GND
MSBINV
ENC
ENC
OF
OGND
D11
D10
D9
OV
DD
D8
D7
D6
D5
OGND
GND
GND
D4
D3
D2
OV
DD
D1
D0
NC
NC
OGND
CLKOUT
OE
3
LTC1745
1745i
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SNR
Signal-to-Noise Ratio
5MHz Input Signal (2V Range)
71
dB
5MHz Input Signal (3.2V Range)
q
71
72.5
dB
30MHz Input Signal (2V Range)
71
dB
30MHz Input Signal (3.2V Range)
72
dB
70MHz Input Signal (2V Range)
70
dB
70MHz Input Signal (3.2V Range)
71.5
dB
SFDR
Spurious Free Dynamic Range
5MHz Input Signal (2V Range)
96.5
dB
5MHz Input Signal (3.2V Range)
q
78
96.5
dB
30MHz Input Signal (2V Range)
93.5
dB
30MHz Input Signal (3.2V Range)
87.5
dB
70MHz Input Signal (2V Range)
78.5
dB
70MHz Input Signal (3.2V Range)
70.5
dB
S/(N + D)
Signal-to-(Noise + Distortion) Ratio
5MHz Input Signal (2V Range)
71
dB
5MHz Input Signal (3.2V Range)
q
71
72.5
dB
30MHz Input Signal (2V Range)
71
dB
30MHz Input Signal (3.2V Range)
72
dB
70MHz Input Signal (2V Range)
69.5
dB
70MHz Input Signal (3.2V Range)
68.5
dB
THD
Total Harmonic Distortion
5MHz Input Signal, First 5 Harmonics (2V Range)
95
dB
5MHz Input Signal, First 5 Harmonics (3.2V Range)
93
dB
30MHz Input Signal, First 5 Harmonics (2V Range)
92
dB
30MHz Input Signal, First 5 Harmonics (3.2V Range)
87
dB
70MHz Input Signal, First 5 Harmonics (2V Range)
77.5
dB
70MHz Input Signal, First 5 Harmonics (3.2V Range)
70
dB
IMD
Intermodulation Distortion
f
IN1
= 4MHz, f
IN2
= 5.1MHz (2V Range)
97
dBc
f
IN1
= 4MHz, f
IN2
= 5.1MHz (3.2V Range)
93
dBc
Sample-and-Hold Bandwidth
R
SOURCE
= 50
240
MHz
The
q
indicates specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25
C. A
IN
= 1dBFS. (Note 5)
DY
A
IC ACCURACY
U
W
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
CM
Output Voltage
I
OUT
= 0
2.29
2.35
2.41
V
V
CM
Output Tempco
I
OUT
= 0
30
ppm/
C
V
CM
Line Regulation
4.75V
V
DD
5.25V
3
mV/V
V
CM
Output Resistance
1mA
I
OUT
1mA
4
(Note 5)
I TER AL REFERE CE CHARACTERISTICS
U
U
U
4
LTC1745
1745i
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
f
SAMPLE(MAX)
Maximum Sampling Frequency
(Note 9)
q
25
MHz
t
1
ENC Low Time
(Note 9)
q
19
20
1000
ns
t
2
ENC High Time
(Note 9)
q
19
20
1000
ns
t
3
Aperture Delay of Sample-and-Hold
0
ns
t
4
Delay to Data Output
C
L
= 10pF (Note 8)
q
0.5
1.5
5
ns
t
5
ENC to CLKOUT Delay
(Note 8)
q
0
1
3
ns
t
6
CLKOUT to Data Delay
(Note 8)
q
0
0.5
ns
t
7
DATA Access Time After OE
C
L
= 5pF (Note 8)
10
25
ns
t
8
BUS Relinquish Time
(Note 8)
10
25
ns
The
q
indicates specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25
C. (Note 5)
TI I G CHARACTERISTICS
U
W
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: All voltage values are with respect to ground with GND
(unless otherwise noted).
Note 3: When these pin voltages are taken below GND or above V
DD
, they
will be clamped by internal diodes. This product can handle input currents
of greater than 100mA below GND or above V
DD
without latchup.
Note 4: When these pin voltages are taken below GND, they will be
clamped by internal diodes. This product can handle input currents of
>100mA below GND without latchup. These pins are not clamped to V
DD
.
Note 5: V
DD
= 5V, f
SAMPLE
= 25MHz, differential ENC/ENC = 2V
P-P
25MHz
sine wave, input range =
1.6V differential, unless otherwise specified.
Note 6: Integral nonlinearity is defined as the deviation of a code from a
straight line passing through the actual endpoints of the transfer curve.
The deviation is measured from the center of the quantization band.
Note 7: Bipolar offset is the offset voltage measured from 0.5 LSB
when the output code flickers between 0000 0000 0000 and
1111 1111 1111.
Note 8: Guaranteed by design, not subject to test.
Note 9: Recommended operating conditions.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IH
High Level Input Voltage
V
DD
= 5.25V
q
2.4
V
V
IL
Low Level Input Voltage
V
DD
= 4.75V
q
0.8
V
I
IN
Digital Input Current
V
IN
= 0V to V
DD
q
10
A
C
IN
Digital Input Capacitance
MSBINV and OE Only
1.5
pF
V
OH
High Level Output Voltage
OV
DD
= 4.75V
I
O
= 10
A
4.74
V
I
O
= 200
A
q
4
V
V
OL
Low Level Output Voltage
OV
DD
= 4.75V
I
O
= 160
A
0.05
V
I
O
= 1.6mA
q
0.1
0.4
V
I
OZ
Hi-Z Output Leakage D11 to D0
V
OUT
= 0V to V
DD
, OE = High
q
10
A
C
OZ
Hi-Z Output Capacitance D11 to D0
OE = High (Note 8)
q
15
pF
I
SOURCE
Output Source Current
V
OUT
= 0V
50
mA
I
SINK
Output Sink Current
V
OUT
= 5V
50
mA
The
q
indicates specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25
C. (Note 5)
DIGITAL I PUTS A D DIGITAL OUTPUTS
U
U
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
DD
Positive Supply Voltage
4.75
5.25
V
I
DD
Positive Supply Current
2V Range, Full-Scale Input
q
76
91
mA
P
DIS
Power Dissipation
2V Range, Full-Scale Input
380
455
mW
OV
DD
Digital Output Supply Voltage
0.5
V
DD
V
The
q
indicates specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25
C. (Note 5)
POWER REQUIRE E TS
W
U
5
LTC1745
1745i
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Nonaveraged, 32768 Point FFT,
Input Frequency = 5MHz,
3.2V Range
Typical INL
Typical DNL
Nonaveraged, 32768 Point FFT,
Input Frequency = 30MHz,
2V Range
Nonaveraged, 32768 Point FFT,
Input Frequency = 30MHz,
3.2V Range
Nonaveraged, 32768 Point FFT,
Input Frequency = 5MHz,
2V Range
Nonaveraged, 32768 Point
2-Tone FFT, Input Frequency =
4MHz and 5.1MHz, 3.2V Range
Nonaveraged, 32768 Point FFT,
Input Frequency = 70MHz,
2V Range
Nonaveraged, 32768 Point
2-Tone FFT, Input Frequency =
4MHz and 5.1MHz, 2V Range
CODE
0
1.0
INL ERROR (LSB)
0.5
0
0.5
1.0
1000
2000
1745 G01
3000
4000
CODE
0
1.0
DNL ERROR (LSB)
0.5
0
0.5
1.0
1000
2000
1745 G02
3000
4000
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
70
80
90
100
110
120
50
40
0
20
2
6
8
12
10
30
4
10
1745 G03
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
70
80
90
100
110
120
50
40
0
20
2
6
8
12
10
30
4
10
1745 G04
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
70
80
90
100
110
120
50
40
0
20
2
6
8
12
10
30
4
10
1745 G05
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
70
80
90
100
110
120
50
40
0
20
2
6
8
12
10
30
4
10
1745 G06
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
70
80
90
100
110
120
50
40
0
20
2
6
8
12
10
30
4
10
1745 G07
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
70
80
90
100
110
120
50
40
0
20
2
6
8
12
10
30
4
10
1745 G08
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
70
80
90
100
110
120
50
40
0
20
2
6
8
12
10
30
4
10
1745 G09
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