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Basic Electronics » AVcc

May 31, 2010
by kgb
kgb's Avatar

HI, Wouldn't we need a low pass filter at the AVcc pin, pin 20, on the MCU, as the datasheet suggests? and why do we need a LPF whenever we are using ADC?



May 31, 2010
by hevans
(NerdKits Staff)

hevans's Avatar

Hi kgb,

I'm glad to see you on our forums asking a lot of great questions. The AVCC pin is the power source the analog to digital converter. Because analog to digital conversions can be particularly susceptible to noise, they recommend you use a low pass filter to try to keep noise away from the ADC. The way we connect the NerdKit we use the same power supply to run the ADC and the chip, and admittedly that might introduce some noise to your conversions, but not enough to be noticeable in the temperature sensor program (particularly after we average many of the readings in software). If you care about having extremely accurate ADC readings you can add a low pass filter to the ADC power supply.


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