Datasheet AD8557 (Analog Devices)

Digitally Programmable Sensor Signal Amplifier Data Sheet AD8557 FEATURES FUNCTIONAL BLOCK DIAGRAM VDD Very low offset voltage: 12 μV maximum over temperature Very low input offset voltage drift: 65 nV/°C maximum VCLAMP VDD A4 High CMRR: 96 dB minimum VNEG R4 P3 R6 Digitally programmable gain and output offset voltage A1 VSS Gain range from 28 to 1300 R1 VDD Qualified for automotive applications VSS P1 Single-wire serial interface R3 A3 Stable with any capacitive load VOUT SOIC and LFCSP packages P2 VDD VSS 2.7 V to 5.5 V operation R2 R5 R7 A2 APPLICATIONS VPOS VDD P4 Automotive sensors VSS Pressure and position sensors DIGIN Precision current sensing
01
Thermocouple amplifiers
0 3-
VSS
01
Industrial weigh scales
06 Figure 1.
Strain gages GENERAL DESCRIPTION
The AD8557 is a zero drift, sensor signal amplifier with digitally also includes a pull-up current source at the input pins and a programmable gain and output offset. Designed to easily and pull-down current source at the VCLAMP pin. Output clamping accurately convert variable pressure sensor and strain bridge set via an external reference voltage allows the AD8557 to drive outputs to a well-defined output voltage range, the AD8557 lower voltage analog-to-digital converters (ADCs) safely and accurately amplifies many other differential or single-ended accurately. sensor outputs. The AD8557 uses the Analog Devices, Inc., When used in conjunction with an ADC referenced to the same proprietary low noise auto-zero and DigiTrim® technologies to supply, the system accuracy becomes immune to normal supply create an accurate and flexible signal processing solution in a voltage variations. Output offset voltage can be adjusted with a compact footprint. resolution of better than 0.4% of the difference between VDD Gain is digitally programmable in a wide range from 28 to 1300 and VSS. A lockout trim after gain and offset adjustment through a serial data interface. Gain adjustment can be fully further ensures field reliability. simulated in circuit and then permanently programmed with The AD8557 is fully specified from −40°C to +125°C. reliable polyfuse technology. Output offset voltage is also digitally Operating from single-supply voltages of 2.7 V to 5.5 V, the programmable and is ratiometric to the supply voltage. AD8557 is offered in an 8-lead SOIC, and a 4 mm × 4 mm, In addition to extremely low input offset voltage and input 16-lead LFCSP. offset voltage drift and very high dc and ac CMRR, the AD8557
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Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION GAIN VALUES OPEN WIRE FAULT DETECTION SHORTED WIRE FAULT DETECTION FLOATING VPOS, VNEG, OR VCLAMP FAULT DETECTION DEVICE PROGRAMMING Digital Interface Initial State Simulation Mode Programming Mode Read Mode Sense Current Programming Procedure Determining Optimal Gain and Offset Codes OUTLINE DIMENSIONS ORDERING GUIDE AUTOMOTIVE PRODUCTS