LTC1292/LTC1297
Single Chip 12-Bit
Data Acquisition Systems
FEATURES
s
s
s
s
s
DESCRIPTIO
s
Single Supply 5V Operation
Power Shutdown After Each Conversion (LTC1297)
Built-In Sample-and-Hold
60kHz Maximum Throughput Rate (LTC1292)
Direct 3-Wire Interface to Most MPU Serial Ports and
All MPU Parallel Ports
Analog Inputs Common Mode to Supply Rails
KEY SPECIFICATIO S
s
s
s
s
Resolution: 12 Bits
Fast Conversion Time: 12µs Max Over Temp
Low Supply Current: 6.0mA
Shutdown Supply Current: 5µA (LTC1297)
The LTC
®
1292/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 5µA, 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
LTCMOS is trademark of Linear Technology Corporation
TYPICAL APPLICATIO
12-Bit Differential Input Data Acquisition System
10000
CS
DIFFERENTIAL
INPUTS
COMMON MODE
RANGE
0V TO 5V
*
V
CC
CLK
LTC1297
1N4148
D
OUT
V
REF
+
+
–
+IN
–IN
GND
SCK
MISO
LT1027
8V TO 40V
1µF
AVERAGE I
CC
(µA)
5V
22µF
TANTALUM
DO
MC68HC11
+
4.7µF
TANTALUM
*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
U
Power Supply Current
vs Sampling Frequency
1000
100
10
1
1
10
100
1k
f
SAMPLE
(Hz)
10k
100k
LTC1297• TA02
U
U
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1
LTC1292/LTC1297
ABSOLUTE
(Notes 1 and 2)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
CS 1
+IN 2
–IN 3
GND 4
8 V
CC
7 CLK
6 D
OUT
5 V
REF
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
LTC1292BI, LTC1292CI,
LTC1292DI ......................................... –40°C to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec.)................ 300°C
ORDER PART NUMBER
LTC1292BIN8 LTC1297BCN8
LTC1292CIN8 LTC1297CCN8
LTC1292DIN8 LTC1297DCN8
LTC1292BCN8
LTC1292CCN8
LTC1292DCN8
N8 PACKAGE
8-LEAD PLASTIC DIP
T
JMAX
= 100°C,
θ
JA
=130°C/W (N8)
J8 PACKAGE
8-LEAD CERAMIC DIP
T
JMAX
= 150°C,
θ
JA
=100°C/W (J8)
LTC1292BCJ8 LTC1297BCJ8
LTC1292CCJ8 LTC1297CCJ8
LTC1292DCJ8 LTC1297DCJ8
OBSOLETE PACKAGE
Consider the N8 Package for Alternate Source
Consult LTC Marketing for parts specified with wider operating temperature ranges.
CO VERTER A D
PARAMETER
Offset Error
Linearity Error (INL)
Gain Error
Minimum Resolution for Which No
Missing Codes are Guaranteed
Analog and REF Input Range
On Channel Leakage Current
(Note 8)
The
q
denotes the specifications
which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
LTC1292B
LTC1297B
MIN TYP MAX
q
q
q
ULTIPLEXER CHARACTERISTICS
CONDITIONS
(Note 4)
(Note 4 & 5)
(Note 4)
LTC1292C
LTC1297C
MIN TYP MAX
±3.0
±0.5
±1.0
12
–0.05V to V
CC
+ 0.05V
LTC1292D
LTC1297D
MIN TYP MAX
±3.0
±0.75
±4.0
12
UNITS
LSB
LSB
LSB
Bits
V
±3.0
±0.5
±0.5
12
(Note 7)
On Channel = 5V
Off Channel = 0V
On Channel = 0V
Off Channel = 5V
q
q
q
q
q
±1
±1
±1
±1
±1
±1
±1
±1
±1
±1
±1
±1
Off Channel Lekage Current
(Note 8)
On Channel = 5V
Off Channel = 0V
On Channel = 0V
Off Channel = 5V
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2
U
µA
µA
µA
µA
W
U
U
W W
W U
W
U
LTC1292/LTC1297
AC CHARACTERISTICS
SYMBOL
f
CLK
t
SMPL
t
CONV
t
CYC
t
dDO
t
dis
t
en
t
hDO
t
f
t
r
t
WHCLK
t
WLCLK
t
suCS
t
WHCS
t
WLCS
C
IN
PARAMETER
Clock Frequency
Analog Input Sample Time
Conversion Time
Total Cycle Time
Delay Time, CLK↓ to D
OUT
Data Valid
Delay Time, CS↑ to D
OUT
Hi-Z
Delay Time, CLK↓ to D
OUT
Enabled
Time Output Data Remains Valid After CLK↓
D
OUT
Fall Time
D
OUT
Rise Time
CLK High Time
CLK Low Time
Setup Time, CS↓ Before CLK↑
(LTC1297 Wakeup Time)
CS High Time Between Data Transfer Cycles
CS Low Time During Data Transfer
Input Capacitance
See Test Circuits
See Test Circuits
V
CC
= 5V (Note 6)
V
CC
= 5V (Note 6)
V
CC
= 5V (Note 6)
V
CC
= 5V (Note 6)
V
CC
= 5V (Note 6)
Analog Inputs On Channel
Analog Inputs Off Channel
Digital Inputs
LTC1292
LTC1297
LTC1292
LTC1297
LTC1292
LTC1297
q
q
The
q
denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C. (Note 3)
LTC1292B/LTC1297B
LTC1292C/LTC1297C
LTC1292D/LTC1297D
MIN
TYP
MAX
(Note 9)
LTC1292
LTC1297
1.5CLK
0.5CLK+5.5µs
12
LTC1292
LTC1297
q
q
q
CONDITIONS
V
CC
= 5V (Note 6)
See Operating Sequence
See Operating Sequence
See Operating Sequence
(Note 6)
See Test Circuits
See Test Circuits
See Test Circuits
UNITS
MHz
1.0
CLK
Cycles
14CLK+2.5µs
14CLK+6µs
160
80
80
130
65
25
300
400
50
5.5
2.5
0.5
14CLK
14CLK+ 5.5µs
100
5
5
pF
pF
pF
130
50
300
150
200
ns
ns
ns
ns
ns
ns
ns
ns
ns
µs
µs
µs
DIGITAL A D DC ELECTRICAL CHARACTERISTICS
SYMBOL
V
IH
V
IL
I
IH
I
IL
V
OH
V
OL
I
OZ
I
SOURCE
I
SINK
PARAMETER
High Level Input Voltage
Low Level Input Voltage
High Level Input Current
Low Level Input Current
High Level Output Voltage
Low Level Output Voltage
High Z Output Leakage
Output Source Current
Output Sink Current
CONDITIONS
V
CC
= 5.25V
V
CC
= 4.75V
V
IN
= V
CC
V
IN
= 0V
V
CC
= 4.75V, I
O
= –10µA
I
O
= 360µA
V
CC
= 4.75V, I
O
= 1.6mA
V
OUT
= V
CC
, CS High
V
OUT
= 0V, CS High
V
OUT
= 0V
V
OUT
= V
CC
q
q
q
q
q
q
q
q
The
q
denotes the specifications which
apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
LTC1292B/LTC1297B
LTC1292C/LTC1297C
LTC1292D/LTC1297D
MIN
TYP
MAX
2.0
0.8
2.5
–2.5
2.4
4.7
4.0
0.4
3
–3
–20
20
U
UNITS
V
V
µA
µA
V
V
V
µA
µA
mA
mA
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3
LTC1292/LTC1297
DIGITAL A D DC ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which
apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
LTC1292B/LTC1297B
LTC1292C/LTC1297C
LTC1292D/LTC1297D
SYMBOL
I
CC
PARAMETER
Positive Supply Current
I
REF
Reference Current
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
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Supply Voltage
10
CLK = 1MHz
T
A
= 25°C
8
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
8
7
6
5
4
SUPPLY CURRENT (µA)
6
4
2
0
4
5
SUPPLY VOLTAGE (V)
4
U W
U
CONDITIONS
CS High
CS Low
CS High Power Shutdown CLK Off
CS High
LTC1292
LTC1297
LTC1297
q
q
q
q
MIN
TYP
6
6
5
10
MAX
12
12
10
50
UNITS
mA
mA
µA
µA
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.
Supply Current vs Temperature
10
9
CLK = 1MHz
V
CC
= 5V
10
9
8
7
6
5
4
3
2
1
LTC1297 Supply Current (Power
Shutdown) vs Temperature
V
CC
= 5V
V
REF
= 5V
CS HIGH
CLK OFF
6
LTC1292/7 G01
3
–50 –30 –10 10 30 50 70 90 110 130
AMBIENT TEMPERATURE (°C)
LTC1292/7 G02
0
50
25
0
75 100
–50 –25
AMBIENT TEMPERATURE (°C)
125
LTC1292/7 G03
12927fb
LTC1292/LTC1297
TYPICAL PERFOR A CE CHARACTERISTICS
LTC1297 Supply Current (Power
Shutdown) vs CLK Frequency
25
V
CC
= 5V
V
REF
= 5V
CS HIGH
CMOS LOGIC LEVELS
20
LINEARITY (LSB = 1/4096
×
V
REF
)
OFFSET (LSB = 1/4096
×
V
REF
)
SUPPLY CURRENT (µA)
15
10
5
0
0
200
600
800
400
CLK FREQUENCY (kHz)
Change in Gain vs
Reference Voltage
0
CHANGE IN GAIN (LSB = 1/4096
×
V
REF
)
–0.2
–0.4
–0.6
–0.8
–1.0
–1.2
0
1
2
3
4
REFERENCE VOLTAGE (V)
5
MAGNITUDE OF OFFSET CHANGE (LSB)
V
CC
= 5V
0.5
0.4
MAGNITUDE OF LINEARITY CHANGE (LSB)
Change in Gain vs Temperature
0.5
MAGNITUDE OF GAIN CHANGE (LSB)
0.25
0.20
0.15
0.10
0.05
V
CC
= 5V
V
REF
= 5V
CLK = 1MHz
0.4
D
OUT
DELAY TIME FROM CLK↓ (ns)
MINIMUM CLK FREQUENCY (MHz)
0.3
0.2
0.1
0
–50
–25
25
50
75 100
0
AMBIENT TEMPERATURE (°C)
* 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).
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U W
LTC1292/7 G04
Unadjusted Offset Voltage vs
Reference Voltage
0.9
V
CC
= 5V
0.8
0.7
0.6
0.5
0.4
V
OS
= 0.250mV
0.3
0.2
0.1
1000
Change in Linearity vs
Reference Voltage
1.25
V
CC
= 5V
1.00
0.75
0.50
0.25
V
OS
= 0.125mV
1
3
2
4
REFERENCE VOLTAGE (V)
5
LTC1292/7 G05
0
0
1
3
4
2
REFERENCE VOLTAGE (V)
5
LTC1292/7 G06
Change in Offset vs Temperature
0.5
V
CC
= 5V
V
REF
= 5V
CLK = 1MHz
Change in Linearity vs
Temperature
V
CC
= 5V
V
REF
= 5V
CLK = 1MHz
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0
–50
–25
25
50
75 100
0
AMBIENT TEMPERATURE (°C)
125
0
–50
–25
25
50
75 100
0
AMBIENT TEMPERATURE (°C)
125
LTC1292/7 G07
LTC1292/7 G08
LTC1292/7 G09
Minimum Clock Rate for
0.1 LSB Error*
250
V
CC
= 5V
200
D
OUT
Delay Time vs Temperature
V
CC
= 5V
150
MSB FIRST DATA
100
LSB FIRST DATA
50
125
–50
–25
25
50
75 100
0
AMBIENT TEMPERATURE (°C)
125
0
–50
–25
25
50
75 100
0
AMBIENT TEMPERATURE (°C)
125
LTC1292/7 G10
LTC1292/7 G11
LTC1292/7 G12
5
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