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MSP430-ADC10: Reading VCC with a voltage reference

Peter Unrein
Prodigy 50 points

Part Number: MSP430-ADC10

Hi! I'd like to sample the onboard voltage references of either 2.5 (REF2_5) or 1.5 volts so that I can measure when my chips VCC gets below a certain threshold.

for example:
I know that If I'm measuring from GND to 3.0 volts and sampling 2.5 volts my ADC10MEM value should be 0x355 or 853. If my vcc drops to 2.8 my ADC10MEM value will be 0x392 or 914. 

I don't have to actually convert these values to a voltage readout the only thing that matters is knowing when the Vcc gets below a set threshold. 

working with a MSP430-EXP430G2 on CSS

  • 0
    TI__Guru**** 202256 points
    Hi Peter,

    This is possible if you use 1.5 V as the reference (SREF1 & REF2_5 = 0) and (Vcc-Vss)/2 as the input channel select (INCH11). You cannot use REF2_5 because its minimum analog supply voltage range is 2.9 V, therefore AVcc values below 2.9 V will begin to affect the reference level. But if Vcc is 3 V then half that is 1.5 V, so during normal operation the ADC reading with 1.5 V reference will be 1024 but once this dips to 956 then you will know that Vcc has dropped to 2.8 V.

    Regards,
    Ryan

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