AD8557ARZ Datasheet, PDF (1/24 Pages) Analog Devices – Digitally Programmable Sensor Signal Amplifier

FEATURES
Very low offset voltage: 12 μV maximum over temperature
Very low input offset voltage drift: 65 nV/°C maximum
High CMRR: 96 dB minimum
Digitally programmable gain and output offset voltage
Gain range from 28 to 1300
Qualified for automotive applications
Single-wire serial interface
Stable with any capacitive load
SOIC_N and LFCSP_VQ packages
2.7 V to 5.5 V operation
APPLICATIONS
Automotive sensors
Pressure and position sensors
Precision current sensing
Thermocouple amplifiers
Industrial weigh scales
Strain gages
GENERAL DESCRIPTION
The AD8557 is a zero drift, sensor signal amplifier with digitally
programmable gain and output offset. Designed to easily and
accurately convert variable pressure sensor and strain bridge
outputs to a well-defined output voltage range, the AD8557
accurately amplifies many other differential or single-ended
sensor outputs. The AD8557 uses the Analog Devices, Inc.
patented low noise auto-zero and DigiTrim® technologies to
create an accurate and flexible signal processing solution in a
compact footprint.
Gain is digitally programmable in a wide range from 28 to 1300
through a serial data interface. Gain adjustment can be fully
simulated in circuit and then permanently programmed with
reliable polyfuse technology. Output offset voltage is also
digitally programmable and is ratiometric to the supply voltage.
In addition to extremely low input offset voltage and input
offset voltage drift and very high dc and ac CMRR, the AD8557
Digitally Programmable
Sensor Signal Amplifier
AD8557
FUNCTIONAL BLOCK DIAGRAM
VDD
VNEG
VPOS
VDD
A1
VSS
VDD
A2
VSS
VCLAMP
R4 ^P3 R6
R1
VDD
P1
R3
A3
P2
R2
R5
VSS
R7
VDD ^P4
DIGIN
A4
VSS
VOUT
VSS
Figure 1.
also includes a pull-up current source at the input pins and a
pull-down current source at the VCLAMP pin. Output
clamping set via an external reference voltage allows the
AD8557 to drive lower voltage ADCs safely and accurately.
When used in conjunction with an ADC referenced to the same
supply, the system accuracy becomes immune to normal supply
voltage variations. Output offset voltage can be adjusted with a
resolution of better than 0.4% of the difference between VDD
and VSS. A lockout trim after gain and offset adjustment
further ensures field reliability.
The AD8557 is fully specified from −40°C to +125°C.
Operating from single-supply voltages of 2.7 V to 5.5 V, the
AD8557 is offered in an 8-lead SOIC_N, and a 4 mm × 4 mm,
16-lead LFCSP_VQ.
Rev. C
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