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TMS320F2809: Bypass Capacitor Value on ADCREFP/M

Part Number: TMS320F2809

Hi Champs,

I know the bypass capacitor for ADCREFP/M should be 2.2uF (ESR : <1.5ohm) as following table.

One of my customer used 10uF for this internal reference circuit.

Is there any side effect if 10uF is used instead of 2.2uF?



  • Steve,

    In terms of performance there should not be an impact.  The only parameter I would have a concern is the wait time after the internal reference is enabled in the customer code.

    I believe that the current DS requirement is 5ms after the ADC/ADC reference is enabled before using the ADC.  In case with 10uF, we can look at F281x DS which had same requirement on the cap, and that device has 10ms wait time.

    There will be no damage if this is not followed, just potential for ADC to operate outside it performance specs in terms of error until the voltage is settled.