MPX2202DP datasheet(520/670 Pages) MOTOROLA

520 / 670 page

AN1586

3–374

Motorola Sensor Device Data

www.motorola.com/semiconductors

ADDITIONAL NOTES

This type of A/D conversion method (one type of A/D

conversion) inherently takes a finite period of time to digitize

the signal (incrementing the pulse train’s high time while

polling the general I/O pin); however, for most sensor

applications the physical phenomenon being measured does

not change quickly (<1 ms) enough to warrant an ultra–fast

A/D conversion process.

An additional advantage of this design is that the

measurement process may be performed only as necessary,

keeping the CPU processing time and overhead minimal.

If an input capture timer channel (TCAP) is available, it may

be configured to detect the logic–level one to logic–level zero

transition of the comparator’s output. When the edge

transition occurs, an interrupt service routine is executed that

stores the pulse train’s high times, calculates the current

pressure, etc. This is typically more convenient and eliminates

the need to poll a general I/O pin every time the pulse train’s

high time is incremented (interrupt subroutine is executed only

when the edge transition occurs).

SUMMARY

Shown above is a minimal component design that can

convert an analog sensor’s output into a digital output. Each

major subsystem (sensor, amplifier, integrator, comparator,

and microcontroller) is explained in detail simultaneously with

a design example. Next the system operation is discussed

including how it works and how to design a desired system

resolution. Finally a flow chart for measuring and calibrating

the sensor’s output is presented.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

MPX2202DP Datasheet(PDF) 520 Page - Motorola, Inc