MPXM2102AS datasheet(167/670 Pages) MOTOROLA

167 / 670 page

MPX12 SERIES

3–21

Motorola Sensor Device Data

www.motorola.com/semiconductors

TEMPERATURE COMPENSATION

Figure 2 shows the typical output characteristics of the

MPX12 series over temperature.

Because this strain gauge is an integral part of the silicon

diaphragm, there are no temperature effects due to differ-

ences in the thermal expansion of the strain gauge and the

diaphragm, as are often encountered in bonded strain gauge

pressure sensors. However, the properties of the strain

gauge itself are temperature dependent, requiring that the

device be temperature compensated if it is to be used over

an extensive temperature range.

Temperature compensation and offset calibration can be

achieved rather simply with additional resistive components,

or by designing your system using the MPX2010D series

sensor.

Several approaches to external temperature compensa-

tion over both – 40 to +125

°C and 0 to +80°C ranges are

presented in Motorola Applications Note AN840.

LINEARITY

Linearity refers to how well a transducer’s output follows

the equation: Vout = Voff + sensitivity x P over the operating

pressure range (Figure 3). There are two basic methods for

calculating nonlinearity: (1) end point straight line fit or (2) a

least squares best line fit. While a least squares fit gives the

“best case” linearity error (lower numerical value), the cal-

culations required are burdensome.

Conversely, an end point fit will give the “worst case” error

(often more desirable in error budget calculations) and the

calculations are more straightforward for the user. Motoro-

la’s specified pressure sensor linearities are based on the

end point straight line method measured at the midrange

pressure.

Figure 2. Output versus Pressure Differential

Figure 3. Linearity Specification Comparison

Figure 4. Cross–Sectional Diagram (not to scale)

SILICONE

DIE COAT

WIRE BOND

LEAD FRAME

DIE

STAINLESS STEEL

METAL COVER

EPOXY

CASE

RTV DIE

BOND

OFFSET

(VOFF)

MAX

POP

SPAN

(VFSS)

PRESSURE (kPA)

ACTUAL

THEORETICAL

LINEARITY

PRESSURE DIFFERENTIAL

0.3

2.0

0.6

4.0

0.9

6.0

1.2

8.0

1.5

PSI

kPa

SPAN

RANGE

(TYP)

OFFSET

(TYP)

VS = 3 Vdc

P1 > P2

–40

°C

+25

°C

+ 125

°C

Figure 4 illustrates the differential or gauge configuration

in the basic chip carrier (Case 344). A silicone gel isolates

the die surface and wire bonds from the environment, while

allowing the pressure signal to be transmitted to the silicon

diaphragm.

The MPX12 series pressure sensor operating characteris-

tics and internal reliability and qualification tests are based

on use of dry air as the pressure media. Media other than

dry air may have adverse effects on sensor performance and

long term reliability. Contact the factory for information re-

garding media compatibility in your application.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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