MAX1452 Просмотр технического описания (PDF) - Maxim Integrated

Номер в каталоге

Компоненты Описание

производитель

MAX1452

Low-Cost Precision Sensor Signal Conditioner

Maxim Integrated 

MAX1452

Low-Cost Precision Sensor

Signal Conditioner

DRIVEN BY TESTER

THREE-STATE

NEED WEAK

PULLUP

THREE-STATE

2ATIM +1 BYTE

TIMES

THREE-STATE

NEED WEAK

PULLUP

DIO 1 1 1 1 1 0 1 0 0 1 1 0 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

HIGH IMPEDANCE

OUT

VALID OUT

Figure 6. Analog Output Timing

The analog signal driven onto the OUT pin is determined

by the value in the ALOC register. The signals are speci-

fied in Table 15.

Test System Configuration

The MAX1452 is designed to support an automated

production test system with integrated calibration and

temperature compensation. Figure 7 shows the imple-

mentation concept for a low-cost test system capable of

testing many transducer modules connected in parallel.

The MAX1452 allows for a high degree of flexibility in

system calibration design. This is achieved by use of

single-wire digital communication and three-state output

nodes. Depending upon specific calibration requirements

one may connect all the OUTs in parallel or connect DIO

and OUT on each individual module.

Sensor Compensation Overview

Compensation requires an examination of the sensor per-

formance over the operating pressure and temperature

range. Use a minimum of two test pressures (e.g., zero

and full-span) and two temperatures. More test pressures

and temperatures result in greater accuracy. A typical

compensation procedure can be summarized as follows:

Set reference temperature (e.g., +25°C):

● Initialize each transducer by loading their respective

registers with default coefficients (e.g., based on mean

values of offset, FSO and bridge resistance) to prevent

overload of the MAX1452.

● Set the initial bridge voltage (with the FSODAC) to

half of the supply voltage. Measure the bridge voltage

using the BDR or OUT pins, or calculate based on

measurements.

● Calibrate the output offset and FSO of the transducer

using the ODAC and FSODAC, respectively.

● Store calibration data in the test computer or MAX1452

EEPROM user memory.

Set next test temperature:

● Calibrate offset and FSO using the ODAC and

FSODAC, respectively.

● Store calibration data in the test computer or MAX1452

EEPROM user memory.

● Calculate the correction coefficients.

● Download correction coefficients to EEPROM.

● Perform a final test.

Sensor Calibration and

Compensation Example

The MAX1452 temperature compensation design corrects

both sensor and IC temperature errors. This enables the

MAX1452 to provide temperature compensation approach-

ing the inherent repeatability of the sensor. An example of

the MAX1452’s capabilities is shown in Figure 8.

A repeatable piezoresistive sensor with an initial offset of

16.4mV and a span of 55.8mV was converted into a com-

pensated transducer (utilizing the piezoresistive sensor

with the MAX1452) with an offset of 0.5000V and a span

of 4.0000V. Nonlinear sensor offset and FSO temperature

errors, which were on the order of 20% to 30% FSO, were

reduced to under ±0.1% FSO. The following graphs show

the output of the uncompensated sensor and the output of

the compensated transducer. Six temperature points were

used to obtain this result.

www.maximintegrated.com

Maxim Integrated │  14

Share Link: