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Data Sheet
FEATURES
Very low offset voltage: 12 μV maximum over temperature Very low input offset voltage drift: 65 nV/°C maximum High CMRR: 96 dB minimum Digitally programmable gain and output offset voltage Gain range from 28 to 1300 Qualified for automotive applications Single-wire serial interface Stable with any capacitive load SOIC and LFCSP packages 2.7 V to 5.5 V operation
APPLICATIONS
Automotive sensors Pressure and position sensors Precision current sensing Thermocouple amplifiers Industrial weigh scales Strain gages
GENERAL DESCRIPTION
The AD8557 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 AD8557 accurately amplifies many other differential or single-ended sensor outputs. The AD8557 uses the Analog Devices, Inc., proprietary low noise auto-zero and DigiTrim® technologies to create an accurate and flexible signal processing solution in a compact footprint.
Gain is digitally programmable in a wide range from 28 to 1300 through a serial data interface. Gain adjustment can be fully simulated in circuit and then permanently programmed with reliable polyfuse 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 offset voltage drift and very high dc and ac CMRR, the AD8557
Digitally Programmable Sensor Signal Amplifier
AD8557
FUNCTIONAL BLOCK DIAGRAM
VDD
VNEG VPOS
VDD A1 VSS
VDD A2 VSS
VCLAMP R4 P3 R6
R1 VDD
P1
R3 A3
P2
R2 R5
VSS R7
VDD P4
DIGIN
A4 VSS
VOUT
06013-001
VSS
Figure 1.
also includes a pull-up current source at the input pins and a pull-down current source at the VCLAMP pin. Output clamping set via an external reference voltage allows the AD8557 to drive lower voltage analog-to-digital converters (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 AD8557 is fully specified from −40°C to +125°C. Operating from single-supply voltages of 2.7 V to 5.5 V, the AD8557 is offered in an 8-lead SOIC, and a 4 mm × 4 mm, 16-lead LFCSP.
Rev. D
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AD8557
TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 5
Thermal Resistance ...................................................................... 5 ESD Caution.................................................................................. 5 Pin Configurations and Function Descriptions ........................... 6 Typical Performance Characteristics ............................................. 7
REVISION HISTORY
5/16—Rev. 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
6/11—Rev. 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
7/10—Rev. A to Rev. B Changes to Features Section and Figure 1..................................... 1 Changes to Figure 45...................................................................... 14 Changes t.