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© Freescale Semiconductor, Inc., 2005. All rights reserved.
AN4010
Rev 1, 05/2005
Freescale Semiconductor
Application Note
Low-Pressure Sensing Using MPX2010
Series Pressure Sensors
by: Memo Romero and Raul Figueroa
Sensor Products Division
Systems and Applications Engineering
INTRODUCTION
This application note presents a design for a low pressure
evaluation board using the Freescale Semiconductor, Inc.
MPX2010 series pressure sensors. By providing large gain
amplification and allowing for package flexibility, this board is
intended to serve as a design-in tool for customers seeking to
quickly evaluate this family of pressure sensors.
The MPX2010 family of pressure sensors appeals to
customers needing to measure small gauge, vacuum, or
differential pressures at a low cost. However, different
applications present design-in challenges for these sensors.
For very low pressure sensing, large signal amplification is
required, with gains substantially larger than what is provided
in Freescale's current integrated pressure sensor portfolio. In
terms of packaging, customers often need more mechanical
flexibility such as smaller size, dual porting or both. In many
cases, customers often lack the engineering resources, time
or expertise to evaluate the sensor. The low-pressure
evaluation board, shown in Figure 1, facilitates the design-in-
process by providing large signal gain and by providing for
different package designs in a relatively small footprint.
CIRCUIT DESCRIPTION
For adequate and stable signal gain and output flexibility, a
two-stage differential op-amp circuit with analog or switch
output is utilized, as shown in Figure 2. The four op-amps are
packaged in a single 14 pin quad package. There are several
features to note about the circuitry.
The first gain stage is accomplished by feeding both
pressure sensor outputs (VS- & VS+) into the non-inverting
inputs of operational amplifiers. These op-amps are used in
the standard non-inverting feedback configuration. With the
condition that Resistors R2=R3, and R1=R4 (as closely as
possible), this configuration results in a gain of G1= R4/R3+1.
The default gain is 101, but there are provisions for easily
changing this value. The signal V (op-amp Pin 7) is then
calculated as:
V
1
= G1*(VS+ - VS-) + Voffset. . . . .Equation (1)
Figure 1. Low Pressure Evaluation Board
