MPXM2102AS datasheet(500/670 Pages) MOTOROLA

500 / 670 page

AN1556

3–354

Motorola Sensor Device Data

www.motorola.com/semiconductors

DESIGN EXAMPLE COMPARISON SUMMARY

The preceding examples show how sources of variation can

affect the overall system resolution. The MPX2010 has

on–chip temperature compensation and calibration circuitry to

reduce device–to–device variations and temperature effects.

Consequently, when designing the fixed–value amplifier

circuitry, the resolution possible with the MPX2010 is almost

four times greater than the same amplifier circuit using an

MPX10. In both examples, both systems’ performance

(Resolution) are optimized to be the best possible, given the

distribution of the sensor device parameters and the other

component variations.

As stated previously if the methodology’s calculations show

that the sensor’s signal will always be within the dynamic

range of the amplifier (and high and low reference voltages of

the A/D), a software calibration may then be implemented to

nullify

any

room

temperature

device–to–device

and

component variations.

It should be noted, however, that this methodology does not

consider how to obtain the best performance from a single

sensor system. Rather, the focus of the methodology is to

obtain

the

best

possible

system

performance

while

considering the distribution of device parameters that result

from manufacturing and other sources of variation. By

considering the sources of variation, the system may then be

mass–produced without individually calibrating the sensor

system hardware. Obviously, if each sensor system is

hand–calibrated, the performance will be better. However, the

hand–calibration also requires additional cost and time when

producing the sensor system.

CONCLUSION

To guarantee a specified performance when designing a

fixed–value circuit for sensor systems, all significant sources

of variation must be considered. By considering the sources

of variation (device–to–device variations, temperature effects,

and component tolerances), the system may be designed so

that the specified performance (resolution) is achieved while

still keeping the sensor’s amplified dynamic range within the

A/D window (or saturation levels of the amplifier). The

specified performance may be achieved in all cases by

applying the methodology described herein. By first calculat-

ing the Minimum Required Span to achieve the required

resolution in all scenarios and then determining if the

remaining dynamic range or headroom is large enough to

accommodate the sources of variation, the methodology

determines if the resolution requirement is feasible. If the

sources of variation are too large, the resolution requirement

may not be attainable. In such a case, the resolution

requirement should be relaxed, or the sources of variation

must be decreased. Finally, once the system is successfully

designed to ensure that the sensor signal will always be within

the dynamic range of the amplifier (and high and low reference

voltages of the A/D), a software calibration may be implement-

ed to nullify any room temperature device–to–device and

component variations.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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