Internal ADC noise

[harry123]

Hi, Im using internal ADC for ADC calculation.

The noise is getting generated for low voltage signal can someone please tell me how to reduce it as im facing the issue of finding the zero crossing in the signal?

[AScha.3]

1. how big is the noise ?  (+/- xx LSB )

2. show the circuit at the adc input.

3. which cpu ?

[harry123]

The input is a sine wave from a function generator with 300mv and 1hz.

Stm32f429 disc1 board

[Tinnagit]

you can use VrefInt to calculate millivolt per bit from 1.21V.

and You should use oversampling which it require more sampling frequency but you will get better accuracy of ADC.

[harry123]

This is the noise that is getting generated.

[Tinnagit]

yes, the oversampling will can help you.

and you should figure out what sampling cycle or sampling time that your system can operate because there is high frequency sampling came with high noise too. so you need to figure out what the value that your system can run on it.

[AScha.3]

Try with a simple input filter:

C1 close to adc-in connector.

[Uwe Bonnes]

There is an application note to reduce noise with the ADC. One aspect in the F4 family is concurrent device activity during sensitive phases during the conversion.

[harry123]

@Uwe Bonnes  can you please tell me how as im new to stm

[Uwe Bonnes]

https://www.st.com/content/ccc/resource/technical/document/application_note/group0/3f/4c/a4/82/bd/63/4e/92/CD00211314/files/CD00211314.pdf/jcr:content/translations/en.CD00211314.pdf