Inner workings of adc

[Michael Wakileh]

Never posted my thoughts....
the method woudn't work because the Ansel bits (which select the channel the sampling cap is connected to) don't allow for the sampling cap to be disconnected from all the channels... too bad...

As much as I looked around I couldn't find a single good resource on how the Adc internals really work... as far as I can guess the Sampling cap comes after the multiplexer or is built into it...

If I ever get the chance to make some pcbs I will be testing a few other ideas I had... will post my results then...

[ScaleRobotics]

The online book from Mikroe explains it with some nice visuals.

http://www.mikroe.com/en/books//picmcubook/ch7/

[Michael Wakileh]

Hi, thanks for the reply. I believe I stumbled upon that image when I started the thread. Together with these 2 attached images (from microchip datasheet), I had tried to figure out where exactly the Sampling cap is located (in the multiplexer?, between multiplexer and adc unit? in the adcunit?)

Currently I believe it may be in the adc, with godone disconnecting it from the multiplexer and connecting it to the successive approximation circuitry (new channel can be selected after godone is set, but sampling of new channel begins only when conversion is complete) .

I also had a few other questions even though they may have no practical application:

For example can the sampling cap be connected to a pin (using Ansel) while ADON is off? Does the Sampling Cap retain its charge when ADON is off?


I guess that led to a useful question as well and I haven't found an answer yet:

Can internal resistance and capacitance of a pic pin be measured using a voltmeter/LC-meter without destroying the pic?

[Michael Wakileh]

Any information regarding the last question would be great to know in advance