1
LTC1292/LTC1297
Single Chip 12-Bit
Data Acquisition Systems
S
FEATURE
D
U
ESCRIPTIO
KEY SPECIFICATIO S
U
U
A
O
PPLICATI
TYPICAL
s
Resolution: 12 Bits
s
Fast Conversion Time: 12
s Max Over Temp
s
Low Supply Current: 6.0mA
s
Shutdown Supply Current: 5
A (LTC1297)
s
Built-In Sample-and-Hold
s
Single Supply 5V Operation
s
60kHz Maximum Throughput Rate (LTC1292)
s
Power Shutdown After Each Conversion (LTC1297)
s
Direct 3-Wire Interface to Most MPU Serial Ports and
All MPU Parallel Ports
s
Analog Inputs Common Mode to Supply Rails
The LTC1292/LTC1297 are data acquisition systems that
contain a 12-bit, switched-capacitor successive approxi-
mation A/D, a differential input, sample-and-hold on the
(+) input, and serial I/O. When the LTC1297 is idle between
conversions it automatically powers down reducing the
supply current to 5
A, typically. The LTC1292 is capable
of digitizing signals at a 60kHz rate and with the device's
excellent AC characteristics, it can be used for DSP appli-
cations. All these features are packaged in an 8-pin DIP
and are made possible using LTCMOS
TM
switched-capaci-
tor technology.
The serial I/O is designed to communicate without external
hardware to most MPU serial ports and all MPU parallel
I/O ports allowing data to be transmitted over three wires.
Because of their accuracy, ease of use and small package
size these devices are well suited for digitizing analog
signals in remote applications where minimum number of
interconnects and power consumption are important.
LTCMOS is trademark of Linear Technology Corporation
12-Bit Differential Input Data Acquisition System
+
DIFFERENTIAL
INPUTS
COMMON MODE
RANGE
0V TO 5V
*
1N4148
V
REF
D
OUT
CLK
V
CC
LTC1297
+IN
GND
CS
IN
LT1027
4.7F
TANTALUM
+
8V TO 40V
1F
22F
TANTALUM
DO
MC68HC11
SCK
MISO
*FOR OVERVOLTAGE PROTECTION LIMIT THE INPUT CURRENT TO 15mA
PER PIN OR CLAMP THE INPUTS TO V
CC
AND GND WITH 1N4148 DIODES.
CONVERSION RESULTS ARE NOT VALID WHEN ANY INPUT IS OVERVOLTAGED
(V
IN
< GND OR V
IN
> V
CC
). SEE SECTION ON OVERVOLTAGE PROTECTION IN
THE APPLICATIONS INFORMATION.
LTC1292/7 TA01
+
5V
f
SAMPLE
(Hz)
10
AVERAGE I
CC
(
A)
100
1000
10000
1
100
10k
LTC1297 TA02
1
10
1k
100k
Power Supply Current
vs Sampling Frequency
2
LTC1292/LTC1297
W
U
U
PACKAGE/ORDER I FOR ATIO
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
(Notes 1 and 2)
Supply Voltage (V
CC
) to GND .................................. 12V
Voltage
Analog and Reference
Inputs..................................... 0.3V to V
CC
+ 0.3V
Digital Inputs ........................................ 0.3V to 12V
Digital Outputs .......................... 0.3V to V
CC
+ 0.3V
Power Dissipation .............................................. 500mW
Operating Temperature Range
LTC1292/LTC1297BC, LTC1292/LTC1297CC,
LTC1292/LTC1297DC ............................ 0
C to 70
C
LTC1292/LTC1297BI, LTC1292/LTC1297CI,
LTC1292/LTC1297DI ........................ 40
C to 85
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec.)................ 300
C
ORDER PART NUMBER
T
JMAX
= 150
C,
JA
=100
C/W (J8)
T
JMAX
= 100
C,
JA
=130
C/W (N8)
CO VERTER A D ULTIPLEXER CHARACTERISTICS
U
U W
(Note 3)
1
2
3
4
TOP VIEW
N8 PACKAGE
8-LEAD PLASTIC DIP
CS
+IN
IN
GND
J8 PACKAGE
8-LEAD CERAMIC DIP
8
7
6
5
V
CC
CLK
D
OUT
V
REF
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
Offset Error
(Note 4)
q
3.0
3.0
3.0
LSB
Linearity Error (INL)
(Note 4 & 5)
q
0.5
0.5
0.75
LSB
Gain Error
(Note 4)
q
0.5
1.0
4.0
LSB
Minimum Resolution for Which No
12
12
12
Bits
Missing Codes are Guaranteed
Analog and REF Input Range
(Note 7)
q
0.05V to V
CC
+ 0.05V
V
On Channel Leakage Current
On Channel = 5V
q
1
1
1
A
(Note 8)
Off Channel = 0V
On Channel = 0V
q
1
1
1
A
Off Channel = 5V
Off Channel Lekage Current
On Channel = 5V
q
1
1
1
A
(Note 8)
Off Channel = 0V
On Channel = 0V
q
1
1
1
A
Off Channel = 5V
LTC1292C
LTC1297C
LTC1292B
LTC1297B
LTC1292D
LTC1297D
LTC1292BIN8
LTC1297BIN8
LTC1292CIN8
LTC1297CIN8
LTC1292DIN8
LTC1297DIN8
LTC1292BCJ8
LTC1297BCJ8
LTC1292CCJ8
LTC1297CCJ8
LTC1292DCJ8 LTC1297DCJ8
LTC1292BCN8 LTC1297BCN8
LTC1292CCN8 LTC1297CCN8
LTC1292DCN8 LTC1297DCN8
For Military Temperature Ranges please contact factory.
3
LTC1292/LTC1297
AC CHARACTERISTICS
(Note 3)
LTC1292B/LTC1297B
LTC1292C/LTC1297C
LTC1292D/LTC1297D
(Note 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IH
High Level Input Voltage
V
CC
= 5.25V
q
2.0
V
V
IL
Low Level Input Voltage
V
CC
= 4.75V
q
0.8
V
I
IH
High Level Input Current
V
IN
= V
CC
q
2.5
A
I
IL
Low Level Input Current
V
IN
= 0V
q
2.5
A
V
OH
High Level Output Voltage
V
CC
= 4.75V, I
O
= 10
A
4.7
V
I
O
= 360
A
q
2.4
4.0
V
V
OL
Low Level Output Voltage
V
CC
= 4.75V, I
O
= 1.6mA
q
0.4
V
I
OZ
High Z Output Leakage
V
OUT
= V
CC
, CS High
q
3
A
V
OUT
= 0V, CS High
q
3
A
I
SOURCE
Output Source Current
V
OUT
= 0V
20
mA
I
SINK
Output Sink Current
V
OUT
= V
CC
20
mA
LTC1292B/LTC1297B
LTC1292C/LTC1297C
LTC1292D/LTC1297D
DIGITAL A D DC ELECTRICAL CHARACTERISTICS
U
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
f
CLK
Clock Frequency
V
CC
= 5V (Note 6)
(Note 9)
1.0
MHz
t
SMPL
Analog Input Sample Time
See Operating Sequence
LTC1292
1.5CLK
LTC1297
0.5CLK+5.5
s
t
CONV
Conversion Time
See Operating Sequence
12
CLK
Cycles
t
CYC
Total Cycle Time
See Operating Sequence (Note 6)
LTC1292
14CLK+ 2.5
s
LTC1297
14CLK+6
s
t
dDO
Delay Time, CLK
to D
OUT
Data Valid
See Test Circuits
q
160
300
ns
t
dis
Delay Time, CS
to D
OUT
Hi-Z
See Test Circuits
q
80
150
ns
t
en
Delay Time, CLK
to D
OUT
Enabled
See Test Circuits
q
80
200
ns
t
hDO
Time Output Data Remains Valid After CLK
130
ns
t
f
D
OUT
Fall Time
See Test Circuits
q
65
130
ns
t
r
D
OUT
Rise Time
See Test Circuits
q
25
50
ns
t
WHCLK
CLK High Time
V
CC
= 5V (Note 6)
300
ns
t
WLCLK
CLK Low Time
V
CC
= 5V (Note 6)
400
ns
t
suCS
Setup Time, CS
Before CLK
V
CC
= 5V (Note 6)
LTC1292
50
ns
(LTC1297 Wakeup Time)
LTC1297
5.5
s
t
WHCS
CS High Time Between Data Transfer Cycles
V
CC
= 5V (Note 6)
LTC1292
2.5
s
LTC1297
0.5
s
t
WLCS
CS Low Time During Data Transfer
V
CC
= 5V (Note 6)
LTC1292
14CLK
LTC1297
14CLK+ 5.5
s
C
IN
Input Capacitance
Analog Inputs On Channel
100
pF
Analog Inputs Off Channel
5
pF
Digital Inputs
5
pF
4
LTC1292/LTC1297
DIGITAL A D DC ELECTRICAL CHARACTERISTICS
U
(Note 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
CC
Positive Supply Current
CS High
LTC1292
q
6
12
mA
CS Low
LTC1297
q
6
12
mA
LTC1297BC, LTC1297CC, LTC1297DC
q
5
10
A
LTC1297BI, LTC1297CI, LTC1297DI
q
5
15
A
LTC1297BM, LTC1297CM, LTC1297DM
I
REF
Reference Current
CS High
q
10
50
A
LTC1292B/LTC1297B
LTC1292C/LTC1297C
LTC1292D/LTC1297D
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
CS High
Power
Shutdown
CLK Off
AMBIENT TEMPERATURE (C)
50
SUPPLY CURRENT (mA)
7
8
9
30
70
LTC1292/7 G02
6
5
30 10
50
90 110
4
3
10
10
130
CLK = 1MHz
V
CC
= 5V
SUPPLY VOLTAGE (V)
4
SUPPLY CURRENT (mA)
4
6
6
LTC1292/7 G01
2
0
5
10
8
CLK = 1MHz
T
A
= 25C
LTC1297 Supply Current (Power
Shutdown) vs Temperature
AMBIENT TEMPERATURE (C)
50
0
SUPPLY CURRENT (
A)
1
3
4
5
10
7
0
50
75
LTC1292/7 G03
2
8
9
6
25
25
100
125
V
CC
= 5V
V
REF
= 5V
CS HIGH
CLK OFF
Supply Current vs Temperature
Supply Current vs Supply Voltage
below GND or one diode drop above V
CC
. Be careful during testing at low
V
CC
levels (4.5V), as high level reference or analog inputs (5V) can cause
this input diode to conduct, especially at elevated temperatures, and cause
errors for inputs near full scale. This spec allows 50mV forward bias of
either diode. This means that as long as the reference or analog input does
not exceed the supply voltage by more than 50mV, the output code will be
correct. To achieve an absolute 0V to 5V input voltage range will therefore
require a minimum supply voltage of 4.950V over initial tolerance,
temperature variations and loading.
Note 8: Channel leakage current is measured after the channel selection.
Note 9: Increased leakage currents at elevated temperatures cause the S/
H to droop, therefore it is recommended that f
CLK
125kHz at 125
C, f
CLK
31kHz at 85
C, and f
CLK
3kHz at 25
C.
The
q
denotes specifications which apply over the operating temperature
range; all other limits and typicals T
A
= 25
C.
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 (unless otherwise
noted).
Note 3: V
CC
= 5V, V
REF
= 5V, CLK = 1.0MHz unless otherwise specified.
Note 4: One LSB is equal to V
REF
divided by 4096. For example, when V
REF
= 5V, 1LSB = 5V/4096 = 1.22mV.
Note 5: Linearity error is specified between the actual end points of the
A/D transfer curve. The deviation is measured from the center of the
quantization band.
Note 6: Recommended operating conditions.
Note 7: Two on-chip diodes are tied to each reference and analog input
which will conduct for reference or analog input voltages one diode drop
5
LTC1292/LTC1297
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
LTC1297 Supply Current (Power
Shutdown) vs CLK Frequency
REFERENCE VOLTAGE (V)
0
LINEARITY (LSB = 1/4096
V
REF
)
0.75
1.00
1.25
4
LTC1292/7 G06
0.50
0.25
0
1
2
3
5
V
CC
= 5V
Change in Gain vs Temperature
* AS THE CLK FREQUENCY IS DECREASED FROM 1MHz, MINIMUM CLK FREQUENCY (
ERROR
0.1LSB) REPRESENTS THE
FREQUENCY AT WHICH A 0.1LSB SHIFT IN ANY CODE TRANSITION FROM ITS 1MHz VALUE IS FIRST DETECTED (NOTE 9).
CLK FREQUENCY (kHz)
0
SUPPLY CURRENT (
A)
15
20
25
800
LTC1292/7 G04
10
5
0
200
400
600
1000
V
CC
= 5V
V
REF
= 5V
CS HIGH
CMOS LOGIC LEVELS
Change in Linearity vs
Reference Voltage
Unadjusted Offset Voltage vs
Reference Voltage
REFERENCE VOLTAGE (V)
1
0.5
0.6
5
LTC1292/7 G05
0.4
0.3
0.1
2
3
4
0.2
0.9
0.8
OFFSET (LSB = 1/4096
V
REF
)
0.7
V
OS
= 0.125mV
V
CC
= 5V
V
OS
= 0.250mV
Change in Gain vs
Reference Voltage
Change in Offset vs Temperature
AMBIENT TEMPERATURE (C)
50
MAGNITUDE OF OFFSET CHANGE (LSB)
0.3
0.4
0.5
50
LTC1292/7 G08
0.2
0.1
0
25
0
25
75
125
100
V
CC
= 5V
V
REF
= 5V
CLK = 1MHz
Change in Linearity vs
Temperature
AMBIENT TEMPERATURE (C)
50
MAGNITUDE OF LINEARITY CHANGE (LSB)
0.3
0.4
0.5
50
LTC1292/7 G09
0.2
0.1
0
25
0
25
75
125
100
V
CC
= 5V
V
REF
= 5V
CLK = 1MHz
D
OUT
Delay Time vs Temperature
REFERENCE VOLTAGE (V)
0
1.2
CHANGE IN GAIN (LSB = 1/4096
V
REF
)
1.0
0.8
0.6
0.4
0.2
0
1
2
3
4
LTC1292/7 G07
5
V
CC
= 5V
AMBIENT TEMPERATURE (C)
50
MAGNITUDE OF GAIN CHANGE (LSB)
0.3
0.4
0.5
50
LTC1292/7 G10
0.2
0.1
0
25
0
25
75
125
100
V
CC
= 5V
V
REF
= 5V
CLK = 1MHz
AMBIENT TEMPERATURE (C)
50
MINIMUM CLK FREQUENCY (MHz)
0.15
0.20
0.25
50
LTC1292/7 G11
0.10
0.05
25
0
25
75
125
100
V
CC
= 5V
Minimum Clock Rate for
0.1 LSB Error*
AMBIENT TEMPERATURE (C)
50
D
OUT
DELAY TIME FROM CLK
(ns)
150
200
250
50
LTC1292/7 G12
100
0
25
0
25
75
125
100
V
CC
= 5V
50
MSB FIRST DATA
LSB FIRST DATA
PDF 
ZIP