MAX1457 Datasheet, PDF (1/12 Pages) Maxim Integrated Products – 0.1%-Accurate Signal Conditioner for Piezoresistive Sensor Compensation

19-1342; Rev 1; 8/98
EVAALVUAAILTAIOBNLEKIT
0.1%-Accurate Signal Conditioner
for Piezoresistive Sensor Compensation
________________General Description
The MAX1457 is a highly integrated analog-sensor sig-
nal processor optimized for piezoresistive sensor cali-
bration and compensation. It includes a programmable
current source for sensor excitation, a 3-bit program-
mable-gain amplifier (PGA), a 12-bit ADC, five 16-bit
DACs, and an uncommitted op amp. Achieving a total
error factor within 0.1% of the sensor’s repeatability
errors, the MAX1457 compensates offset, full-span out-
put (FSO), offset TC, FSO TC, and full-span output non-
linearity of silicon piezoresistive sensors.
The MAX1457 calibrates and compensates first-order
temperature errors by adjusting the offset and span of
the input signal via digital-to-analog converters (DACs),
thereby eliminating quantization noise. If needed, resid-
ual higher-order errors are then compensated using lin-
ear interpolation of the first-order coefficients stored in
a look-up table (in external EEPROM).
The MAX1457 integrates three traditional sensor-
manufacturing operations into one automated process:
• Pretest: Data acquisition of sensor performance under
the control of a host test computer.
• Calibration and Compensation: Computation and storage
(in an external EEPROM) of calibration and compensation
coefficients determined from transducer pretest data.
• Final Test: Verification of transducer calibration and
compensation, without removal from a pretest socket.
Analog outputs are provided for both pressure and tem-
perature. A general-purpose, uncommitted op amp is also
included on-chip to increase the overall circuit gain, or to
facilitate the implementation of a 2-wire, 4–20mA transmit-
ter. The serial interface is compatible with MicroWire™
and SPI™, and directly connects to an external EEPROM.
Additionally, built-in testability features of the MAX1457
facilitate manufacturing and calibration of multiple sensor
modules, thus lowering manufacturing cost.
Although optimized for use with piezoresistive sensors,
the MAX1457 may also be used with other resistive
sensor types (i.e., accelerometers and strain gauges)
with the addition of a few external components.
_______________________Customization
Maxim can customize the MAX1457 for unique require-
ments. With a dedicated cell library of more than 90
sensor-specific functional blocks, Maxim can quickly pro-
vide customized MAX1457 solutions. Contact Maxim for
additional information.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
SPI is a trademark of Motorola, Inc.
MicroWire is a trademark of National Semiconductor Corp.
____________________________Features
o High Accuracy (within ±0.1% of sensor’s
repeatable errors)
o Compensates Offset, Offset TC, FSO, FSO TC,
Temperature/Pressure Nonlinearity
o Rail-to-Rail^® Analog Output for Calibrated,
Temperature-Compensated Pressure
Measurements
o Programmable Sensor Excitation Current
o SPI/MicroWire-Compatible Serial Interface
o Fast Signal-Path Settling Time (<1ms)
o Accepts Sensor Outputs from 5mV/V to 30mV/V
o Pin-Compatible with MCA7707
_______________Ordering Information
PART
TEMP. RANGE PIN-PACKAGE
MAX1457CWI
0°C to +70°C
28 Wide SO
MAX1457CCJ
0°C to +70°C
32 TQFP
MAX1457C/D
0°C to +70°C
Dice*
Ordering Information continued at end of data sheet.
Note: Contact the factory for customized solutions.
*Dice are tested at T_A = +25°C.
Pin Configurations appear at end of data sheet.
Functional Diagram
ISRC
BDRIVE
INP
INM
AGND
MCS
ECS
ECLK
EDI
EDO
LINDACREF
AMP+
AMP-
V_DD
V_DD
BIAS
GENERATOR
MAX1457
OSCILLATOR
PGA
V_DD
V_SS
12-BIT ADC
SERIAL
EEPROM
INTERFACE
V_DD
A=1
A=1
V_{BDRIVE A = 1}
V_SS
NBIAS
FADJ
FOUT
VOUT
LINDAC
FSOTCDAC
OTCDAC
OFSTDAC
FSODAC
LINOUT
FSOTCOUT
VBBUF
AMPOUT
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