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How long to wait after configuring adc?

Question asked by rick stuart on Mar 10, 2016
Latest reply on Mar 10, 2016 by Kerry Zhou

Hi,

I'm multiplexing a processor pin between a digital-out (SPI/Clock) and an analog-in.  Every time I switch to the analog-in I make about a dozen test reading separated by 100ms.  Every time the reading start high and drop.  Not stabilizing for 3 or 4 reading.  That's 300ms to 400ms of waiting!  I scoped the processor pin and looked at many events.  The voltage during the analog-in phase is rock-steady-flat. That leaves the processor.

 

So, what's going on inside the processor?  Why does the processor's ADC feature take hundreds of milliseconds to stabilize?

 

-thanks

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