MAX1457AWI Maxim Integrated Products, MAX1457AWI Datasheet

MAX1457AWI

Manufacturer Part Number

MAX1457AWI

Description

Manufacturer

Maxim Integrated Products

Datasheet

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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:

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.

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.

19-1342; Rev 1; 8/98

________________General Description

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.

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.

For small orders, phone 408-737-7600 ext. 3468.

_______________________Customization

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.

________________________________________________________________ Maxim Integrated Products

for Piezoresistive Sensor Compensation

0.1%-Accurate Signal Conditioner

____________________________Features

_______________Ordering Information

Ordering Information continued at end of data sheet.

* Dice are tested at T

Pin Configurations appear at end of data sheet.

Note:

MAX1457CWI

MAX1457CCJ

MAX1457C/D

LINDACREF

High Accuracy (within ±0.1% of sensor’s

repeatable errors)

Compensates Offset, Offset TC, FSO, FSO TC,

Temperature/Pressure Nonlinearity

Rail-to-Rail

Temperature-Compensated Pressure

Measurements

Programmable Sensor Excitation Current

SPI/MicroWire-Compatible Serial Interface

Fast Signal-Path Settling Time (<1ms)

Accepts Sensor Outputs from 5mV/V to 30mV/V

Pin-Compatible with MCA7707

BDRIVE

AGND

AMP+

AMP-

ECLK

PART

ISRC

MCS

EDO

INM

ECS

INP

EDI

Contact the factory for customized solutions.

12-BIT ADC

INTERFACE

EEPROM

SERIAL

Analog Output for Calibrated,

= +25°C.

TEMP. RANGE

0°C to +70°C

Functional Diagram

MAX1457

PGA

OSCILLATOR

GENERATOR

BDRIVE

BIAS

28 Wide SO

32 TQFP

Dice*

PIN-PACKAGE

A = 1

NBIAS

FADJ

FOUT

VOUT

LINDAC

FSOTCDAC

OTCDAC

OFSTDAC

FSODAC

LINOUT

FSOTCOUT

VBBUF

AMPOUT

Related parts for MAX1457AWI

MAX1457AWI Summary of contents

Page 1

... 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. ________________________________________________________________ Maxim Integrated Products For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468. 0.1%-Accurate Signal Conditioner ____________________________Features High Accuracy (within ± ...

Page 2

Signal Conditioner for Piezoresistive Sensor Compensation ABSOLUTE MAXIMUM RATINGS Supply Voltage ......................................-0. All other pins ....................................(V SS Continuous Power Dissipation (T = +70°C) A 28-Pin Wide SO (derate 12.50mW/°C above +70°C) ..........1W ...

Page 3

Piezoresistive Sensor Compensation ELECTRICAL CHARACTERISTICS (continued +5V 0V +25°C, unless otherwise noted PARAMETER SYMBOL ANALOG-TO-DIGITAL CONVERTER ADC Differential Nonlinearity Conversion Time ADC Resolution OUTPUTS (LINDAC, FSOTCDAC) Voltage Swing Current Drive ...

Page 4

Signal Conditioner for Piezoresistive Sensor Compensation ______________________________________________________________Pin Description PIN NAME SO TQFP 1 28 INP Positive Sensor Input. Input impedance > INM Negative Sensor Input. Input impedance > AMP+ Positive Input of General-Purpose Operational Amplifier ...

Page 5

Piezoresistive Sensor Compensation _______________Detailed Description The MAX1457 provides an analog amplification path for the sensor signal and a digital path for calibration and temperature correction. Calibration and correction are achieved by varying the offset and gain of a program- ...

Page 6

Signal Conditioner for Piezoresistive Sensor Compensation Two adjustments are required for FSO calibration. First set the coarse gain by digitally selecting the PGA gain. Then calibrate the bridge current by writing a 16-bit calibration coefficient word to the FSO ...

Page 7

Piezoresistive Sensor Compensation Pressure Nonlinearity Correction The MAX1457 corrects pressure nonlinearity in an ana- log fashion by providing a resistive feedback path (resistor R in Figure 4) from a buffered main output LIN (LINOUT pin) to the current source ...

Page 8

Signal Conditioner for Piezoresistive Sensor Compensation R ISRC 50k BDRIVE 0.1 F 0.1 F SENSOR +5V +5V EEPROM 93C66 SO CLK ORG LINDACREF 0.1 F *OPTIONAL PULL-UP RESISTOR Figure 5. Basic Ratiometric ...

Page 9

Piezoresistive Sensor Compensation Figure 6. Basic 2-Wire 4–20mA Configuration _______________________________________________________________________________________ 0.1%-Accurate Signal Conditioner LIN FSO - TC FSO - TC OFFSET - OFFSET - FSO - DAC 16-BIT DAC 16-BIT DAC 16-BIT DAC 16-BIT DAC 16-BIT 9 ...

Page 10

Signal Conditioner for Piezoresistive Sensor Compensation ECS[1:N], MCS[1:N] DIGITAL MULTIPLEXER ECS1 +5V VOUT DVM ECLK EDI EDO Figure 7. Automated Test System Concept 7) Perform curve-fitting to test data. 8) Based on a curve-fit algorithm, calculate up to 120 ...

Page 11

Piezoresistive Sensor Compensation Table 1. MAX1457 Sensor Calibration and Compensation Typical Uncompensated Input (Sensor) Offset . . . . . . . . . . . . . . . . . . . . . . . . ...

Page 12

... Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1998 Maxim Integrated Products © 1998 Maxim Integrated Products TRANSISTOR COUNT: 17534 SUBSTRATE CONNECTED TO V Ordering Information (continued) PART MAX1457AWI MAX1457ACJ TOP VIEW V DD AGND NBIAS AMPOUT 1 ...

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