Zero Drift, Digital Programmable

Instrumentation Amplifier

Preliminary Data Sheet

AD8231

Rev. PrC

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FEATURES

Digitally programmable gain

G= 1, 2, 4, 8, 16, 32, 64, 128

Software or pin programmable

Excellent temperature performance

Specified from −40°C to +125°C

50 nV/°C max input offset drift

10 ppm/°C max gain drift

Excellent dc performance

122 dB min CMR, G = 128

25 μV max input offset voltage

100 pA max bias current

0.7 uV p-p (0.1 Hz to 10 Hz)

Good ac performance

Gain Bandwidth Product 1 MHz

Slew Rate 0.7 V/μs

Rail-to-rail input and output

Shutdown/Multiplex

Additional uncommitted op amp

Supply range: 3.0V to 5.5V

APPLICATIONS

Pressure and Strain Transducers

Thermocouples and RTDs

Programmable Instrumentation

Industrial Controls

Weigh Scales

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/ºC.

Because of the autozero input stage, maximum input offset is 25

uV and maximum input offset drift is just 50 nV/ºC. CMRR is

also guaranteed over temperature: 80 dB for G=1, increasing to

122 dB at a gain of 128. Voltage noise is just 0.7 uV p-p (0.01

Hz to 10 Hz).

+VS

-VS

SDN

A1

A2

AD8231

REF

OUT1

OUT2

+IN

-IN

P

N

A0

WR

Figure 1. AD8231 Functional Diagram

The AD8231 also includes an uncommitted op amp which can

be used for additional gain, differential signal driving or

filtering. Like the in amp, the op amp has an autozero

architecture, rail to rail input, and rail to rail output.

The AD8231 includes a shutdown feature that reduces current

to 1 uA and makes the amplifier output high impedance. This

allows easy multiplexing of multiple amplifiers without

additional switches.

The AD8231 is specified over the extended industrial

temperature range of -40°C to +125°C. It is available in a 4mm

x 4mm 16-Lead LFCSP (Chip Scale) package.