Zero Drift, Digitally Programmable

Instrumentation Amplifier

Data Sheet

AD8231

Rev. C

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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/μs 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

IN-AMP

LOGIC

NC

1

–INA

2

+INA

3

NC

4

12

11

OUTA

10

REF

9

OP

AMP

AD8231

Figure 1.

Category

High

Performance

Low

Cost

High

Voltage

Mil

Grade

Low

Power

Digital

Gain

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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.