3–347
Motorola Sensor Device Data
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THE EXAMPLE CIRCUIT
Referring to Figure 1, both pressure sensors are interfaced
to the same amplifier circuit topology. In Tables 1 and 2, the
relevant characteristics for the MPX10 and MPX2010 show
the
device–to–device
and
Additionally, the tolerances on the voltage regulator and the
temperature
variations.
resistors that establish the gain and dc voltage level shift
(VREF) are considered in the methodology. The voltage
regulator’s device–to–device tolerance is
±
5%, and each
resistor’s tolerance is
±
1%.
–
+
–
+
Vin
5 V REG. (
±
5%)
IN
GND
OUT
VS
RREF1
S–
S+
X1
MPX10 OR MPX2010
R1
R2
R3
R4
U1
U1
LM33272
VO TO A/D
RREF2
VREF
Figure 1. MPX10/MPX2010 Circuit Schematic
Table 1. MPX10 Variation Characteristics
Characteristic (VS = 5.0 V)
Symbol
Min
Typ
Max
Unit
Pressure Range
POP
VFSS
Voff
TCVFSS
TCVoff
0
—
10
kPa
Full–Scale Span
33
58
83
mV
Zero Pressure Offset
0
33
58
mV
Temperature Coefficient of Full–Scale Span (see Note 1)
–0.22
–0.19
–0.16
%/
°
C
Temperature Coefficient of Offset (see Note 2)
—
±
15
—
μ
V/
°
C
Note 1: Slope of end–point straight line fit to full–scale span at –40
°
C and +125
°
C relative to 25
°
C
Note 2: Slope of end–point straight line fit to zero pressure offset at –40
°
C and +125
°
C relative to 25
°
C
Table 2. MPX2010 Variation Characteristics
Characteristic (VS = 5.0 V)
Symbol
Min
Typ
Max
Unit
Pressure Range
POP
VFSS
Voff
TCVFSS
TCVoff
0
—
10
kPa
Full–Scale Span
12
12.5
13
mV
Zero Pressure Offset
–0.5
—
0.5
mV
Temperature Effect on Full–Scale Span (see Note 1)
–1.0
—
1.0
%FSS
Temperature Effect on Offset (see Note 2)
–0.5
—
0.5
mV
Note 1: Maximum change in full–scale span at 0
°
C and 85
°
C relative to 25
°
C
Note 2: Maximum change in offset at 0
°
C and 85
°
C relative to 25
°
C
The amplifier topology used is a two–operational amplifier
gain stage that has all the desirable characteristics of a
differential–signal instrumentation amplifier:
high input impedance
low output impedance
differential to single–ended conversion of the input signal
high gain capability
dc level shifting capability
For good common mode rejection, the following resistor
ratios are used:
R4
R3
With this simplification, the transfer function of the amplifier
is
VO
(
R4
R3
R1
R2
1
)
(S
– S–)
VREF
F
Freescale Semiconductor, Inc.
n
.