AN672/1104

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Rev. 2.0

AN672

APPLICATION NOTE

OPTIMIZING THE ST6 A/D CONVERTER ACCURACY

INTRODUCTION

When using the internal Analog to Digital Converter of the ST62 family and maximum A/D con-

verter accuracy is required, it is desirable to filter out any noise present on the analog input,

voltage reference of the A/D converter. Good decoupling must be made with capacitors on the

eration of the micro-controller itself.

Finally, when enough time is available, it is highly recommended to make several successive

A/D conversions and take an average of the results. This is the most effective way to get the

most accuracy out of the ST6 family A/D converter.

The following code fragment demonstrates a burst of 256 successive measurements, after

which the average is put into the accumulator. The whole routine takes approximately 30 milli-

seconds with an 8 MHz clock. When less time is available, it is of course possible to reduce the

number of conversions: 8, 16 or 32 conversions also give good results, although the most con-

versions give the best results.

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