AD8231_1 Datasheet, PDF (1/24 Pages) Analog Devices – Zero Drift, Digitally Programmable Instrumentation Amplifier

Zero Drift, Digitally Programmable
Instrumentation Amplifier
AD8231
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 6 V
Dual-supply range: ±1.5 V to ±3 V
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/°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.
FUNCTIONAL BLOCK DIAGRAM
NC ¹
–INA ²
+INA ³
LOGIC
IN-AMP
NC ⁴
AD8231
OP
AMP
12 _+VS
11
–V_S
10 _OUTA
9 _REF
Figure 1.
Table 1. Instrumentation and Difference Amplifiers by
Category
High
Low
Performance Cost
High
Mil
Low
Digital
Voltage Grade Power Gain
AD8221
AD8220¹
AD623¹ AD628
AD8553¹ AD629
AD620 AD627¹ AD8231¹
AD621
AD8250
AD8222
AD8224¹
AD524
AD526
AD624
AD8251
AD8555¹
AD8556¹
AD8557¹
1 _{Rail-to-rail output.}
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.
Rev. A
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