AN3137 datasheet(35/42 Pages) STMICROELECTRONICS

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AN3137

Methods for precision improvement

Doc ID 16983 Rev 3

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4.5

Design rules for minimizing errors

ADC precision can only be significantly improved if external influences on the measurement

are minimized. Therefore any precision improvement method also includes rules for correct

design.

Main design rules for minimizing design errors:

●

Grounding of analog/digital power:

–

star topology

●

VDDA, VSSA filtering:

–

RC, LC filtering

–

avoid noise from noisy digital power

●

VREF selection - offset, value, precision:

–

reference voltage source precision and stability matched to application precision

requirements and ADC capability

–

reference voltage source value and precision in line with the expected measured

range

●

Source impedance vs. input impedance knowledge:

–

use input buffers for measured signal

–

impedance in relation with required conversion speed (proper sampling time)

●

External preamplifier usage:

–

for low (and also high) level signals

–

amplifier speed and precision properties

–

amplifier dependency on frequency

●

Select appropriate ADC mode, speed, trigger

●

Software methods: averaging, FFT, … (see Chapter 4.3: Software methods)

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