Digitally Programmable Sensor Signal Amplifier Data Sheet AD8557 FEATURES FUNCTIONAL BLOCK DIAGRAM VDD Very low offset voltage: 12 V maximum over temperature Very low input offset voltage drift: 65 nV/C maximum VCLAMP VDD A4 High CMRR: 96 dB minimum P3 VNEG R4 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 P2 SOIC and LFCSP packages VDD VSS R2 2.7 V to 5.5 V operation R5 R7 A2 APPLICATIONS P4 VPOS VDD Automotive sensors VSS Pressure and position sensors DIGIN Precision current sensing Thermocouple amplifiers VSS Industrial weigh scales 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 40C to +125C. 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 Rev. D Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 20072016 Analog Devices, Inc. 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Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. 06013-001AD8557 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Theory of Operation ...................................................................... 14 Applications ....................................................................................... 1 Gain Values ................................................................................. 15 Functional Block Diagram .............................................................. 1 Open Wire Fault Detection ....................................................... 16 General Description ......................................................................... 1 Shorted Wire Fault Detection ................................................... 16 Revision History ............................................................................... 2 Floating VPOS, VNEG, or VCLAMP Fault Detection ......... 16 Specif icat ions ..................................................................................... 3 Device Programming ................................................................. 16 Absolute Maximum Ratings ............................................................ 5 Outline Dimensions ....................................................................... 21 Thermal Resistance ...................................................................... 5 Ordering Guide .......................................................................... 22 ESD Caution .................................................................................. 5 Automotive Products ................................................................. 22 Pin Configurations and Function Descriptions ........................... 6 Typical Performance Characteristics ............................................. 7 REVISION HISTORY 5/16Rev. C to Rev. D Changed CP-16-10 to CP-16-20 .................................. Throughout Changes to Figure 3 and Table 5 ..................................................... 6 Updated Outline Dimensions ....................................................... 21 Changes to Ordering Guide .......................................................... 22 6/11Rev. B to Rev. C Added EPAD Note to Figure 3 and Table 5 ................................... 6 Changes to Open Wire Fault Detection Section and Table 8 ... 16 7/10Rev. A to Rev. B Changes to Features Section and Figure 1 ..................................... 1 Changes to Figure 45 ...................................................................... 14 Changes to Simulation Mode Section and Programming Mode Section................................................................................... 18 Changes to Ordering Guide .......................................................... 22 Added Automotive Products Section .......................................... 22 1/08Rev. 0 to Rev. A Changes to Theory of Operation Section .................................... 14 Changes to Determining Optimal Gain and Offset Codes Section .................................................................................. 20 5/07Revision 0: Initial Version Rev. D Page 2 of 24