MPX700AP 查看數據表（PDF） - Motorola => Freescale
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MPX700AP Datasheet PDF : 8 Pages
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TEMPERATURE COMPENSATION
Figure 2 shows the typical output characteristics of the
MPX700 series over temperature.
The X–ducer piezoresistive pressure sensor element is a
semiconductor device which gives an electrical output signal
proportional to the pressure applied to the device. This de-
vice uses a unique transverse voltage diffused semiconduc-
tor strain gauge which is sensitive to stresses produced in a
thin silicon diaphragm by the applied pressure.
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
80
70
60
50
40
30
20
10
0
PSI 0
kPa
MPX700
VS = 3 Vdc
P1 > P2
– 40°C
+ 125°C
+ 25°C SPAN
RANGE
(TYP)
20
40
60
80
140
280
420
560
PRESSURE DIFFERENTIAL
OFFSET
(TYP)
100
700
Figure 2. Output versus Pressure Differential
MPX700 SERIES
or by designing your system using the MPX2700 series
sensors.
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. Motorola’s
specified pressure sensor linearities are based on the end
point straight line method measured at the midrange
pressure.
70
LINEARITY
50
ACTUAL
40
30
20
THEORETICAL
SPAN
(VFSS)
10
OFFSET
0
(VOFF)
0
MAX POP
PRESSURE (kPA)
Figure 3. Linearity Specification Comparison
SILICONE GEL
DIE COAT
ÉÉÉÉÉÉÉÉÉÉÉ WIRE BOND
DIFFERENTIAL/GAUGE
DIE
P1
STAINLESS STEEL
METAL COVER
EPOXY
CASE
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ LEAD FRAME
DIFFERENTIAL/GAUGE ELEMENT
DIE
BOND
P2
SILICONE GEL
DIE COAT
ABSOLUTE
DIE
P1
ÉÉÉÉÉÉÉÉÉÉÉ WIRE BOND
STAINLESS STEEL
METAL COVER
EPOXY
CASE
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ LEAD FRAME
ABSOLUTE ELEMENT
DIE
BOND
P2
Figure 4. Cross–Sectional Diagrams (not to scale)
Figure 4 illustrates the differential or gauge configuration
in the basic chip carrier (Case 344–15). A silicone gel iso-
lates the die surface and wire bonds from the environment,
while allowing the pressure signal to be transmitted to the sil-
icon diaphragm.
The MPX700 series pressure sensor operating character-
istics 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.
Motorola Sensor Device Data
3
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