Digital circuitry inside and outside the
device generates EMI which might affect the accuracy of analog measurements. If conversion
accuracy is critical, the noise level can be reduced by applying the following
techniques:
- Keep analog signal paths as short as possible.
- Make sure analog tracks run over the analog ground plane
- Keep analog tracks well away from
high-speed switching digital tracks.
- If any port pin is used as a digital output, it mustn’t switch while a conversion is
in progress.
- Place bypass capacitors as close to
VCC and GND pins as possible.
When high ADC accuracy is required it is recommended to use ADC Noise Reduction Mode. A
good system design with properly placed, external bypass capacitors does reduce the need
for using ADC Noise Reduction Mode.