MPL115A1

Sensors

Freescale Semiconductor

3

Pressure

Figure 1. Uncompensated Pressure Sensor Schematic

Compensation

The pressure compensation for MPL115A1 is based on a 2-dimensional, second order polynomial based on Microsystems

mst_trimlib library.

The 10-bit compensated pressure output, Pcomp, is calculated as follows:

Pcomp = a0 + (b1 + c11*Padc + c12*Tadc) * Padc + (b2 + c22*Tadc) * Tadc

Where:

Padc is the 10-bit pressure output of the MPL115A1 ADC,

Tadc is the 10-bit temperature output of the MPL115A1 ADC,

a0 is the pressure offset coefficient,

b1 is the pressure sensitivity coefficient,

c11 is the pressure linearity (2nd order) coefficient,

c12 is the coefficient for temperature sensitivity coefficient (TCS),

b2 is the 1st order temperature offset coefficient (TCO),

c22 is the 2nd order temperature offset coefficient.

Ideally, Pcomp will produce a value of 0 with an input pressure of 50 kPa and will produce a full-scale value of 1023 with an input

pressure of 115 kPa.

Diff

Amp

Temp

Sensor

ADC

DIN

GND

VDD

DOUT

Temperature

Pressure

Coefficient

Storage

ADDR

ADDR

ADDR

ADDR

ADDR

SPI

Interface

SHDN

CS

CAP

SCLK

Diff

Amp

Temp

Sensor

ADC

DIN

GND

VDD

DOUT

Temperature

Pressure

Coefficient

Storage

ADDR

ADDR

ADDR

ADDR

ADDR

ADDR

ADDR

ADDR

SPI

Interface

SHDN

CS

CAP

SCLK

VDD

CAP

SHDN

DIN

CS

DOUT

GND

SCLK

μC

1

μF

1

μF

Microcontroller