RE: ADC Sampling Frequency Selection
2009/08/10 21:17:05
(permalink)
Tom,

Some of the details of your ADC set up are not very clear. Assuming that you have opted of Automatic Sampling (ASAM=1), what is the Tad that has been chosen?

For the sake of an example, let us assume that the required sampling rate is 200kHz to sample a 100kHz input. Now, in case you want to sample as well as convert the sampled values at 200kHz, then, each sample would require (1/200k) = 5us. So, if the trigger source is chosen as TMR3, then the triggers have to be atleast 5us spaced apart. Further, if the 10 bit ADC is being employed, 12Tad s are required for converting one channel.

So, 12Tad=5us => 1Tad = 0.416us

=> ADCS = 0.416us/25ns ~= 17

Thus, the sampling and conversion depends on the Tad as well as the triggering rate.

I hope this helps you.