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ADC Hold and Sample

Discussion in 'Microcontrollers, Programming and IoT' started by Hoobbyy_Engineer, Jun 25, 2017.

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  1. Hoobbyy_Engineer

    Hoobbyy_Engineer

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

    Regards,
    Nil
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,270
    2,718
    Jan 21, 2010
    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.
     
  3. Hoobbyy_Engineer

    Hoobbyy_Engineer

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    May 21, 2017
    So the correct parameter to find this charging time for the capacitor is Acquisition Time,right?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,270
    2,718
    Jan 21, 2010
    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 likes this.
  5. Hoobbyy_Engineer

    Hoobbyy_Engineer

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    May 21, 2017
    Thanks,Steve.
     
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