MAX1454_11 Datasheet, PDF(8/25 Page) Maxim Integrated Products – Precision Sensor Signal Conditioner with Overvoltage Protection

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MAX1454

Precision Sensor Signal Conditioner

with Overvoltage Protection

Detailed Description

The MAX1454 is a highly integrated analog sensor

signal conditioner targeted for automotive applications.

The device 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 cal-

ibration of offset and span with integrated 16-bit DACs,

allowing sensors to be truly interchangeable.

The device architecture includes a programmable sen-

sor excitation, a 32-step PGA, a 2K x 8 bits internal flash

memory, four 16-bit DACs, and an on-chip temperature

sensor. In addition to offset and span compensation, the

device provides a unique temperature-compensation

method for offset TC and FSO TC, which was developed

to provide a remarkable degree of flexibility while minimiz-

ing manufacturing costs.

The device uses four 16-bit DACs (offset, FSO, offset TC,

and FSO TC) with coefficients ranging from 0x0000 to

0xFFFF. The offset DAC and FSO DAC are referenced to

VDDX (76FV resolution when VDDX = 5V). The offset TC

DAC and FSO TC DAC are referenced to the bridge volt-

age (38FV resolution when bridge voltage is 2.5V).

The user can select from one to 110 temperature points

to compensate their sensor. This allows the latitude

to compensate a sensor with a simple 1st-order linear

correction or to match an unusual temperature curve.

Programming up to 110 independent 16-bit flash mem-

ory locations corrects performance in 1.5NC temperature

increments, over a range of -40NC to +125NC. 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. For full temperature compensation, the sensor and

the device must be at the same temperature. In cases

where the sensor is at a different temperature than the

device, the device can use the sensor excitation voltage

to provide 1st-order temperature compensation.

The single-pin, multiplexed, serial digital input/output

(DIO) communication architecture, and the ability to time-

share its activity with the sensorâs output signal, enables

output sensing and calibration programming on a single

line.

The device allows complete calibration and sensor veri-

fication to be performed at a single test station. Once

calibration coefficients have been stored in the device, the

customer can retest to verify performance as part of a

regular QA audit, or to generate final test data on indi-

vidual sensors.

The device (Figure 1) provides an analog amplifica-

tion path for the sensor signal. It also uses an analog

architecture for 1st-order temperature correction. A

digitally controlled analog path is then used for nonlin-

ear temperature correction. Calibration and correction

is achieved by varying the offset and gain of a PGA,

and by varying the sensor bridge excitation current or

voltage. The PGA utilizes a switched-capacitor CMOS

VDDX

OVERVOLTAGE,

UNDERVOLTAGE, AND VDDX

REVERSE-VOLTAGE

LDO

VDD

PROTECTION

VDDX

IRO

DAC

MAX1454

IN+

OUT

OUT/DIO

IN-

PGA

FAULT

DETECTION

BDR

CURRENT

SOURCE

TEMP

SENSOR

8-BIT

ADC

5V DIO

DIGITAL

VDDF

INTERFACE

AND

FLASH

MEMORY

VDDX

VBDR

GND

Figure 1. Functional Diagram

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