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ADC Hold and Sample

Hoobbyy_Engineer

May 21, 2017
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May 21, 2017
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Hello Everyone,
Do all microcontroller ADC implement hold and sample circuitry internally?Or should I have to provide it externally?

Regards,
Nil
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
25,510
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25,510
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

May 21, 2017
13
Joined
May 21, 2017
Messages
13
So the correct parameter to find this charging time for the capacitor is Acquisition Time,right?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
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25,510
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.
 
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