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MSP430FR6879 : input ADC protection with Vin > VCC

Alessandro Zecchi
Prodigy 20 points

Hi,

the input of ADC is a a 0-3V signal.

The ref of the ADC is internally set at 2V and the AVCC of the uC is 2.7V.


1) because Vin > AVCC, is an input protection needed in order to avoid damages? Is e series resistor enough?

2) If Vin > Vref =2V the ADC value is anyway 2^12 (full-scale value) ?

Thank you very much for your support

  • 0
    Guru 74080 points

    Hi Alessandro!

    Alessandro Zecchi said:
    1) because Vin > AVCC, is an input protection needed in order to avoid damages? Is e series resistor enough?

    Yes, a series resistor can be sufficient, but it can introduce errors. Furthermore your circuitry must be able to sink the current that flows into the pin. And keep the maximum continuous diode current in mind.

    Alessandro Zecchi said:
    2) If Vin > Vref =2V the ADC value is anyway 2^12 (full-scale value) ?

    Yes, correct. If Vin >= Vref, the output value is 2^12 - 1.

    Dennis

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