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What value resistor is recommended to place in series with ADC input as part of low bandpass filter?

Question asked by injunear on May 16, 2013
Latest reply on May 16, 2013 by Zhe Tian

Somewhere I read that if noise is a possibility on the input of an ADC channel, it is a good idea to place an RC filter between the analog source and the MCU input.


I am using the KL25Z Freedom board. I think I read that there should be a .01 cap to ground and a (possibly?) 50 ohm or less resistor in series with the input.

 

Is this mentioned in the Freescale literature anywhere, and, if so, what values are recommended? Also, how might a 33 ohm resistor, for instance, affect the ADC timing?


Thank you.


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