Detailed Description

The MAX1455 provides amplification, calibration, and tem-

perature compensation to enable an overall performance

approaching the inherent repeatability of the sensor. The

fully analog signal path introduces no quantization noise

in the output signal while enabling digitally controlled

trimming with the integrated 16-bit DACs. The MAX1455

includes four selectable high/low clipping limits set in dis-

crete 50mV steps from 0.1V/4.9V to 0.25V/4.75V. Offset

and span can be calibrated to within ±0.02% of span.

The MAX1455 architecture includes a programmable

sensor excitation, a 16-step PGA, a 768-byte (6144 bits)

internal EEPROM, four 16-bit DACs, an uncommitted op

amp, and an on-chip temperature sensor. The MAX1455

also provides a unique temperature compensation strat-

egy that was developed to provide a remarkable degree

of flexibility while minimizing testing costs.

The customer can select from 1 to 114 temperature

points to compensate their sensor. This allows the

latitude to compensate a sensor with a simple first-

order linear correction or match an unusual tempera-

ture curve. Programming up to 114 independent 16-bit

EEPROM locations corrects performance in 1.5°C tem-

perature increments over a range of -40°C to +125°C.

For sensors that exhibit a characteristic temperature

performance, a select number of calibration points can

be used with a number of preset values that define the

temperature curve. The sensor and the MAX1455 should

be at the same temperature during calibration and use.

This allows the electronics and sensor errors to be com-

pensated together and optimizes performance. For appli-

cations where the sensor and electronics are at different

temperatures, the MAX1455 can use the sensor bridge as

an input to correct for temperature errors.

The single pin, serial DIO communication architecture

and the ability to timeshare its activity with the sensor’s

output signal enables output sensing and calibration

programming on a single line by parallel connecting OUT

and DIO. The MAX1455 provides a Secure-Lock feature

that allows the customer to prevent modification of sen-

sor coefficients and the 52-byte user-definable EEPROM

data after the sensor has been calibrated. The Secure-

Lock feature also provides a hardware override to enable

factory rework and recalibration by assertion of logic high

on the UNLOCK pin.

PIN

NAME

FUNCTION

1, 15, 16

TEST1,

TEST3,

TEST2

2

OUT

Analog Output. Internal voltage nodes can be accessed in digital mode. OUT can be parallel

connected to DIO. Bypass OUT to ground with a 0.1µF capacitor to reduce output noise.

3

INP

Positive Input. Can be swapped to INM by the Configuration register.

4

BDR

Bridge Drive Output

5

INM

Negative Input. Can be swapped to INP by the Configuration register.

6

Negative Supply Voltage

7

8

AMP+

Auxiliary Op Amp Positive Input

9

AMPOUT

Auxiliary Op Amp Output

10

AMP-

Auxiliary Op Amp Negative Input

11

12

UNLOCK

and enable serial communication.

13

DIO

Digital Input Output. Single-pin serial communication port. There are no internal pullups on DIO.

14

TEST4

Test Pin. Do not connect.

MAX1455

Low-Cost Precision Sensor Signal Conditioner

www.maximintegrated.com

Maxim Integrated │ 5

Pin Description