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MSP430F47197 - Capacitor value requirement for Pin8 (AVcc), Pin 64 (DVcc2), Pin92 (DVcc1)

Daichi Tanaka
Prodigy 80 points

    There are no specific suggestion in the User or Hardware manual for MSP430F47197 for capacitor value for the following AVcc and DVcc : Pin8, Pin64, Pin 92.  

Question:

0) We are planning to use a 0.1uF ceramic cap, is this sufficient in design?

1) Does TI have default recommendation of the capacitor value to use on these Vcc pins as a suggestion? (I know it depends on design but all design is always based on suggestion, then improving from the suggestion)

2) How much noise is allowed on the Vcc lines?? (or how much Vpp noise can the power supply take? (typically manufacturers allow 50mVpp but I could not locate any information regarding this)

3)  Are there any noise concerns we should be aware of from the Vcc lines when using 16MHz internal CLK?

Regards,

D.T.

  • 0
    Guru 227245 points

    Except for DAC output (if available), there is not much current drawn from AVCC. So it is a good idea to decouple it form DVCC with a series resistor (10 to 100Ohm) and a capacitor (100nF ceramic and 10µF tantalum are a really good combo).
    It's also a good idea to route AVSS separately form DVSS to the power supply. This keeps GND ripples caused by GND current away from teh analog circuitry.
    For DVCC, 100nF are a good start, but something much larger (47µF at least) should be somewhere near, to compensate for the supply line impedance.

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