Zero-Drift, Digitally Programmable Sensor Signal Amplifier Data Sheet AD8555 FEATURES FUNCTIONAL BLOCK DIAGRAM VDD Very low offset voltage: 10 V maximum over temperature Very low input offset voltage drift: 60 nV/C maximum VCLAMP VDD A5 High CMRR: 96 dB minimum P3 VNEG R4 R6 Digitally programmable gain and output offset voltage A1 VSS Single-wire serial interface R1 VDD Open and short wire fault detection VSS VDD P1 Low-pass filtering RF A3 R3 VOUT Stable with any capacitive load A4 P2 Externally programmable output clamp voltage for driving VDD VSS FILT/ low voltage ADCs R2 DIGOUT VSS R5 R7 LFCSP-16 and SOIC-8 packages A2 VPOS P4 VDD 2.7 V to 5.5 V operation 40C to +125C operation VSS DAC APPLICATIONS Pressure and position sensors VSS Thermocouple amplifiers Industrial weigh scales Figure 1. Precision current sensing Strain gages GENERAL DESCRIPTION The AD8555 is a zero-drift, sensor signal amplifier with In addition to extremely low input offset voltage and input digitally programmable gain and output offset. Designed to offset voltage drift and very high dc and ac CMRR, the AD8555 easily and accurately convert variable pressure sensor and strain also includes a pull-up current source at the input pins and a bridge outputs to a well-defined output voltage range, the pull-down current source at the VCLAMP pin. This allows AD8555 also accurately amplifies many other differential or open wire and shorted wire fault detection. A low-pass filter single-ended sensor outputs. The AD8555 uses the ADI function is implemented via a single low cost external capacitor. patented low noise auto-zero and DigiTrim technologies to Output clamping set via an external reference voltage allows the AD8555 to drive lower voltage ADCs safely and accurately. create an incredibly accurate and flexible signal processing solution in a very compact footprint. When used in conjunction with an ADC referenced to the same Gain is digitally programmable in a wide range from 70 to 1,280 supply, the system accuracy becomes immune to normal supply through a serial data interface. Gain adjustment can be fully voltage variations. Output offset voltage can be adjusted with a simulated in-circuit and then permanently programmed with resolution of better than 0.4% of the difference between VDD proven and reliable poly-fuse technology. Output offset voltage and VSS. A lockout trim after gain and offset adjustment is also digitally programmable and is ratiometric to the supply further ensures field reliability. voltage. The AD8555 is fully specified over the extended industrial temperature range of 40C to +125C. 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. Rev. B 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 20042015 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Technical Support www.analog.com 04598-0-001AD8555 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Open Wire Fault Detection ....................................................... 20 Applications ....................................................................................... 1 Shorted Wire Fault Detection ................................................... 20 Functional Block Diagram .............................................................. 1 Floating VPOS, VNEG, or VCLAMP Fault Detection ......... 20 General Description ......................................................................... 1 Device Programming ................................................................. 20 Revision History ............................................................................... 2 Filtering Function ....................................................................... 26 Electrical Specifications ................................................................... 3 Driving Capacitive Loads .......................................................... 26 Absolute Maximum Ratings ............................................................ 7 RF Interference ........................................................................... 27 ESD Caution .................................................................................. 7 Single-Supply Data Acquisition System .................................. 27 Pin Configurations and Function Descriptions ........................... 8 Using the AD8555 with Capacitive Sensors ........................... 28 Typical Performance Characteristics ........................................... 10 Outline Dimensions ....................................................................... 29 Theory of Operation ...................................................................... 18 Ordering Guide .......................................................................... 29 Gain Values .................................................................................. 19 REVISION HISTORY 2/15Rev. A to Rev. B Changes to Applications Section .................................................... 1 Changes to Table 5 ............................................................................ 8 Changes to Figure 3 .......................................................................... 9 Added Table 6 Renumbered Sequentially .................................... 9 Changes to Figure 64 ...................................................................... 29 Updated Outline Dimensions ....................................................... 29 Changes to Ordering Guide .......................................................... 29 6/09Rev. 0 to Rev A Changes to General Description .................................................... 1 Changes to Figure 3 and Table 5 ..................................................... 8 Updated Outline Dimensions ....................................................... 28 Changes to Ordering Guide .......................................................... 28 4/04Revision 0: Initial Version Rev. B Page 2 of 29