AD8555:  Digitally Programmable Sensor Signal Zero-Drift Amplifier

The AD8555 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 AD8555 also accurately amplifies many other differential or single-ended sensor outputs. The AD8555 uses the ADI 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 1,280 through a serial data interface. Gain adjustment can be fully simulated in-circuit and then permanently programmed with proven and reliable poly-fuse 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 off-set voltage drift and very high dc and ac CMRR, the AD8555 also includes a pull-up current source at the input pins and a pull-down current source at the VCLAMP pin. This 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 AD8555 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 AD8555 is fully specified over the extended industrial temperature range of −40°C to +125°C. Operating from single-supply voltages of 2.7 V to 5.5 V, the AD8555 is offered in the narrow 8-lead SOIC package and the 4 mm × 4 mm 16-lead LFCSP.