MPXM2102AS datasheet(531/670 Pages) MOTOROLA

531 / 670 page

AN1660

3–385

Motorola Sensor Device Data

www.motorola.com/semiconductors

TCR — Temperature coefficient of bridge resistance;

shaped by a Table that accounts for cold temperature

non–linearity’s

TCR2 — Temperature coefficient of contact resistance;

shaped by a Table that accounts for cold temperature

non–linearity’s

TCS — Temperature coefficient of Span; shaped by a Table

that accounts for cold temperature non–linearity’s

RPH — Bridge Resistance (RS1 and RS3) modified by

pressure and temperature

ROH — Offset Component of Bridge Resistors RS1 and RS3

RPL — Bridge Resistance (RS2 and RS4) modified by

pressure and temperature

ROL — Offset Component of Bridge Resistors RS2 and RS4

KB — Bias Constant; adjusts KP for bias voltage effects of

span compensation network (MPX2000 and MPX5000

series sensors)

KBT — Bias Constant; adjusts KO for bias voltage effects of

span compensation network (MPX2000 and MPX5000

series sensors)

GAIN — Instrumentation amplifier gain; differential gain

(MPX5000 series)

ROFF — Offset resistance; determines value of RS13

(MPX5000 series)

After these calculations are made, the final bridge resis-

tance calculation is performed in the circuit section. The value

for bridge resistors RS1 and RS3 is RPH + ROH. Bridge resis-

tors RS2 and RS4 are equal to RPL–ROL.

CIRCUIT

Three circuits are used to model the three sensor families,

one each for the Uncompensated series, MPX2000 series,

and MPX5000 series sensors. Schematics that are derived

from the circuit netlists are shown in Figures 1, 2, and 3. They

are discussed beginning with the Uncompensated series,

which is the least complex.

Uncompensated Series:

The Uncompensated Series sensors (MPX10, MPX50, and

MPX100) are modeled as Wheatstone bridges. In the configu-

ration that is shown in Figure 1, resistors RS2 and RS4

decrease in value as pressure is applied. Similarly, RS1 and

RS3 increase in value as pressure is applied. Resistors RS5

and RS7 are contact resistors. They represent real physical

resistors that are used to make contact to the bridge. Resistors

RS6 and RS8 are included to satisfy PSPICE’s requirement

for no floating nodes. That’s it. The netlist in this model is quite

simple. The hard part is calculating the values for RS1, RS2,

RS3, and RS4.

Figure 1. MPX10 and 100 PSPICE Compound Coefficient Model

NOTES:

* TEMPERATURE SENSITIVE

* * TEMPERATURE & PRESSURE SENSITIVE

RS4

475

RS1

475

RS2

475

RS3

475

RS8

1000MEG

RS7

675

RS5

750

RS6

1000MEG

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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