Datasheet

AD8556
Rev. A | Page 3 of 28
GENERAL DESCRIPTION
The AD8556 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 AD8556 accurately amplifies many other differential or
single-ended sensor outputs. The AD8556 uses the Analog
Devices, Inc. patented low noise, auto-zero and DigiTrim®
technologies to create an incredibly accurate and flexible
signal processing solution in a very compact footprint.
Gain is digitally programmable in a wide range from 70 to
1280 through a serial data interface. Gain adjustment can
be fully simulated in-circuit and then permanently pro-
grammed with reliable polyfuse technology. Output offset
voltage is also digitally programmable and is ratiometric to
the supply voltage. The AD8556 also features internal EMI
filters on the VNEG, VPOS, FILT and VCLAMP pins.
In addition to extremely low input offset voltage, low input offset
voltage drift, and very high dc and ac CMRR, the AD8556 also
includes a pull-up current source at the input pins and a pull-
down current source at the VCLAMP pin, which allows open
wire and shorted wire fault detection. A low-pass filter function
is implemented via a single low cost external capacitor. Output
clamping set via an external reference voltage allows the AD8556
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 AD8556 is fully specified from −40°C to +140°C.
Operating from single-supply voltages of 4.5 V to 5.5 V, the
AD8556 is offered in the 8-lead SOIC_N and 4 mm × 4 mm
16-lead LFCSP_VQ.