MPXM2102AS datasheet(154/670 Pages) MOTOROLA

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Motorola Sensor Device Data

www.motorola.com/semiconductors

Motorola Pressure Sensors

INTRODUCTION

Motorola pressure sensors combine advanced piezoresistive sensor architecture with integrated circuit technology to offer a

wide range of pressure sensing devices for automotive, medical, consumer and industrial applications. Selection versatility

includes choice of:

Pressure Ranges in PSI

Application Measurements

0 to 1.45, 0 to 6, 0 to 7.3, 0 to 14.5, 0 to 29, 0 to 75, 0 to 100,

Absolute, Differential, Gauge

0 to 150 psi.

Sensing Options

Package Options

Uncompensated, Temperature Compensated/Calibrated,

• Basic Element, Ported Elements for specific measurements

and Signal Conditioned (with on–chip amplifiers)

• Surface Mount and Through Hole, Low Profile packages

THE BASIC STRUCTURE

The Motorola pressure sensor is designed utilizing a

monolithic silicon piezoresistor, which generates a changing

output voltage with variations in applied pressure. The

resistive element, which constitutes a strain gauge, is ion

implanted on a thin silicon diaphragm.

Applying pressure to the diaphragm results in a resistance

change in the strain gauge, which in turn causes a change in

the output voltage in direct proportion to the applied

pressure. The strain gauge is an integral part of the silicon

diaphragm, hence there are no temperature effects due to

differences in thermal expansion of the strain gauge and the

diaphragm. The output parameters of the strain gauge itself

are temperature dependent, however, requiring that the

device be compensated if used over an extensive tempera-

ture range. Simple resistor networks can be used for narrow

temperature ranges, i.e., 0

°C to 85°C. For temperature

ranges from – 40

°C to +125°C, more extensive compensa-

tion networks are necessary.

MOTOROLA’S LOCALIZED SENSING ELEMENTS

Excitation current is passed longitudinally through the

resistor (taps 1 and 3), and the pressure that stresses the

diaphragm is applied at a right angle to the current flow. The

stress establishes a transverse electric field in the resistor

that is sensed as voltage at taps 2 and 4, which are located

at the midpoint of the resistor (Figure 3a).

The transducer (Figure 3) uses a single element eliminat-

ing the need to closely match the four stress and tempera-

ture sensitive resistors that form a distributed Wheatstone

bridge design. At the same time, it greatly simplifies the

additional circuitry necessary to accomplish calibration and

temperature compensation. The offset does not depend on

matched resistors but instead on how well the transverse

voltage taps are aligned. This alignment is accomplished in

a single photolithographic step, making it easy to control,

and is only a positive voltage, simplifying schemes to zero

the offset.

Figure 3. X–ducer

™ Sensor Element — Top View

PIN #

1. GROUND

2. +VOUT

3. VS

4. –VOUT

ETCHED

DIAPHRAGM

BOUNDARY

TRANSVERSE

VOLTAGE STRAIN

GAUGE RESISTOR

ACTIVE

ELEMENT

S+

S –

VOLTAGE

TAPS

ETCHED

DIAPHRAGM

BOUNDARY

TRANSVERSE

VOLTAGE STRAIN

GAUGE RESISTOR

ACTIVE ELEMENT

HAS FOUR

P– RESISTORS

S+

S –

PIN #

1. GROUND

2. +VOUT

3. VS

4. –VOUT

Figure 3a. Localized Sensing Element

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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