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ADC sample time

Filipe Teixeira
Prodigy 235 points
Other Parts Discussed in Thread: TMS320F28069

Hello,

I am trying to sample several ADC channels at about 300KHz using TMS320F28069.

I was reading the document http://focus.ti.com/lit/ug/spruge5b/spruge5b.pdf and in page 11 and 12 it has the times for the ADC conversion.

On top of page 12, it says that the RC time constant is 2ns. Can someone explain how do you get that values? Because 3.450k*1.6n=5.52ns

In my case, since I have specified a ACQPS of 6, I have a sample window of 116.67ns, it is enough for the RC of 2ns. I know that value will depend on the external circuit. but assuming that I have a similar one to the example on page 12.

I would really like to know how to obtain the RC=2ns?

Thanks,

Filipe Teixeira