ADC Hold and Sample

[Hoobbyy_Engineer]

Hello Everyone,
Do all microcontroller ADC implement hold and sample circuitry internally?Or should I have to provide it externally?

Regards,
Nil

 

[(*steve*)]

No -- not really. Yes, possibly.

But it's far better to read the specs of the micro-controller that you're using to make sure.

An ATMEGA 328, for example has an input capacitance (14pF from memory) that is allowed to charge for 2 clock cycles (again, from memory) prior to it being read. If the signal is expected to vary significantly within this 2 clock cycle period, then for best accuracy you'll need an external sample and hold.

 

[Hoobbyy_Engineer]

So the correct parameter to find this charging time for the capacitor is Acquisition Time,right?

 

[(*steve*)]

That's one important one.

If you're using atmel chips, check out the Avr127 application note. Even if you're not it still may be helpful.

 

[Hoobbyy_Engineer]

Thanks,Steve.