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Zero Drift, Digitally Programmable
Instrumentation Amplifier
Data Sheet
AD8231
Rev. C Document Feedback
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FEATURES
Digitally/pin-programmable gain
G = 1, 2, 4, 8, 16, 32, 64, or 128
Specified from −40°C to +125°C
50 nV/°C maximum input offset drift
10 ppm/°C maximum gain drift
Excellent dc performance
80 dB minimum CMR, G = 1
15 µV maximum input offset voltage
500 pA maximum bias current
0.7 µV p-p noise (0.1 Hz to 10 Hz)
Good ac performance
2.7 MHz bandwidth, G = 1
1.1 V/s slew rate
Rail-to-rail output
Shutdown/multiplex
Extra op amp
Single-supply range: 3 V to 5 V
Dual-supply range: ±1.5 V to ±2.5 V
Qualified for automotive applications
APPLICATIONS
Pressure and strain transducers
Thermocouples and RTDs
Programmable instrumentation
Industrial controls
Weigh scales
Automotive controls
FUNCTIONAL BLOCK DIAGRAM
06586-001
IN-AMP
LOGIC
NC
1
–INA
2
+IN
A
3
NC
4
+V
S
12
–V
S
11
OUTA
10
REF
9
A2
16
A1
15
A0
14
CS
13
SDN
5
+INB
6
–INB
7
OUTB
8
OP
AMP
AD8231
Figure 1.
Table 1. Instrumentation and Difference Amplifiers by
Category
High
Performance
Low
Cost
High
Voltage
Mil
Grade
Low
Power
Digital
Gain
AD8221 AD623
1
AD628 AD620 AD627
1
AD8231
1
AD8220
1
AD8553
1
AD629 AD621 AD8250
AD8222 AD524 AD8251
AD8224
1
AD526 AD8555
1
AD624 AD8556
1
AD8557
1
1
Rail-to-rail output.
GENERAL DESCRIPTION
The AD8231 is a low drift, rail-to-rail, instrumentation amplifier
with software-programmable gains of 1, 2, 4, 8, 16, 32, 64, or 128.
The gains are programmed via digital logic or pin strapping.
The AD8231 is ideal for applications that require precision
performance over a wide temperature range, such as industrial
temperature sensing and data logging. Because the gain setting
resistors are internal, maximum gain drift is only 10 ppm/°C for
gains of 1 to 32. Because of the auto-zero input stage, maximum
input offset is 15 μV and maximum input offset drift is just
50 nV/°C. CMRR is 80 dB for G = 1, increasing to 110 dB at
higher gains.
The AD8231 also includes an uncommitted op amp that can be
used for additional gain, differential signal driving, or filtering.
Like the in-amp, the op amp has an auto-zero architecture, rail-
to-rail input, and rail-to-rail output.
The AD8231 includes a shutdown feature that reduces current
to a maximum of 1 μA. In shutdown, both amplifiers also have
a high output impedance, which allows easy multiplexing of
multiple amplifiers without additional switches.
The AD8231 is specified over the extended industrial tempera-
ture range of −40°C to +125°C. It is available in a 4 mm × 4 mm
16-lead LFCSP.
