Industry’s First Digitally Programmable, Signal-Conditioning Auto-Zero Amplifier

AD8555 Block
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Norwood, MA –Dec. 9, 2003– AD8555 offers designers a high-accuracy, zero-drift, turnkey solution to program both gain and offset, allowing for greater design flexibility and lower costs in automotive, medical, and industrial process control applications.

Analog Devices Inc. today unveiled the industry's first digitally programmable, signal-conditioning auto-zero amplifier for strain-bridge and other sensors that are widely used in automotive, medical, industrial and communication applications. Within the new chip, ADI has integrated a full range of amplifier, comparator, resistor, trimpot and buffer functionality into a tiny SOIC or 4 mm by
4 mm chipscale package (CSP), providing a complete path from a sensor to analog-to-digital (A/D) converter. This allows systems designers to automatically, under software control, eliminate variations between sensors. Sensor outputs can be digitally programmed for gain and output offset voltage. Prior to the ADI solution engineers relied on devices that had lower accuracy and less stability and involved manual adjustments that were difficult, time consuming and expensive.

With flexible controls enabled by a one-wire serial interface, the AD8555 offers designers many advantages over typical discrete solutions, including zero drift, programmable gain, a very small footprint and lower cost. By using ADI's patented low-noise auto-zero and DigiTrim(TM) technologies, the chip accurately converts differential and single-ended sensor outputs to a well-defined output voltage range, effectively rejecting common mode noise in the process.

The gain and offset adjustment can be simulated in-circuit before being permanently programmed. The chip also offers extensive fault detection (open and short wire and data integrity) to ensure high reliability. In addition, users can easily add a low-pass filter and clamp the maximum output level to protect low voltage A/D converter inputs.

The AD8555's unique combination of precision performance and
functionality in a very compact footprint make it an ideal solution for automotive pressure sensor applications, such as brake, fuel and manifold pressure sensing. It is also suitable for myriad other automotive, industrial and medical applications that rely on high performance process control circuitry, including leak-down pressure detection, resistance temperature detectors, infrared thermopile
sensors and ECG/EKG monitors.

The AD8555 offers integrated low-pass filtering, open and shorted wire fault detection, and output clamp voltage capability — ideal for driving low-voltage analog-to-digital converters. In addition, the AD8555 offers a read-back function to verify correct programming, and a trim lockout function to assure field reliability. By integrating
these features, the AD8555 allows users to manage sensor outputs easily and cost effectively.

The AD8555 has 10-uV max input offset voltage over temperature, 50-nV/degrees C max input offset drift, and 96-dB common mode rejection, resulting in high dc accuracy. Gain is digitally programmable with high resolution over a wide range from 70 to 1280 through a single-wire interface. Output offset voltage is digitally programmed and ratiometric to the supply voltage. The AD8555 allows gain and offset adjustment to be simulated in-circuit before being permanently programmed with reliable poly-fuse trim technology. The amplifier can also drive high capacitive loads.

The AD8555 is currently sampling in 8-lead SOIC or 16-lead LFCSP packaging. The device is priced at $2.80 and $2.90, respectively, per unit in 1,000-piece quantities.

Analog Devices, Inc. Tel: 800-ANAL-OGD (800-262-5643)
For more information, please visit:
Product Brochure.

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