MPX2700A SERIES

3

Motorola Sensor Device Data

LINEARITY

Linearity refers to how well a transducer’s output follows

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

pressure range. There are two basic methods for calculating

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

squares best line fit (see Figure 3). While a least squares fit

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

the calculations 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. Motorola’s

specified pressure sensor linearities are based on the end

point straight line method measured at the midrange

pressure.

Figure 2. Linearity Specification Comparison

LEAST

SQUARE

DEVIATION

PRESSURE (% FULLSCALE)

0

50

100

END POINT

STRAIGHT LINE FIT

EXAGGERATED

PERFORMANCE

CURVE

LEAST SQUARES FIT

STRAIGHT LINE

DEVIATION

OFFSET

ON–CHIP TEMPERATURE COMPENSATION and CALIBRATION

F i g u r e 3 s h o w s t h e o u t p u t c h a r a c t e r i s t i c s o f t h e

MPX2700A series at 25

°C. The output is directly proportional

to the differential pressure and is essentially a straight line.

The effects of temperature on Full–Scale Span and Offset

are very small and are shown under Operating Characteris-

tics.

Figure 3. Output versus Pressure Differential

Figure 4. Cross–Section of Differential Pressure

Sensor Die in Its Basic Package (Not to Scale)

SILICONE

DIE COAT

WIRE BOND

LEAD

FRAME

DIE

STAINLESS STEEL

METAL COVER

RTV DIE

BOND

THERMOPLASTIC CASE

P1

P2

50

40

30

20

10

– 5

20

140

40

280

60

420

100

700

SPAN

RANGE

(TYP)

OFFSET

PSI

kPa

VS = 10 V

TA = 25°C

P1 > P2

MAX

TYP

MIN

0

80

560

Figure 4 shows the cross section of the Motorola MPX

pressure sensor die in the chip carrier package. A silicone

gel isolates the die surface and wire bonds from harsh

environments, while allowing the pressure signal to be

transmitted to the silicon diaphragm. MPX2700A series

pressure sensor operating characteristics and internal reli-

ability 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 regarding media

compatibility in your application.