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MSP430F Internal ADC reference voltage oscillation

Raja sekaran
Intellectual 270 points

Hai,

 In our application we are using MSP430 series for measuring temperature and presure with internal reference.

When ever input 3.3V oscillating the reference volage also oscillating reading variation was to high during input voltage oscillation.

Can you please explain is ADC reference will varry with respect to input oscillation (~20 to 60 mV of input oscillation)

 

Regards,

Rajasekaran

 

  • 0
    Guru 46710 points

    Raja sekaran said:
     In our application we are using MSP430 series

    msp430 series are more than 400 various ICs having various ADC's. Please be specific - provide exact part number.

    Raja sekaran said:
    the reference volage also oscillating reading variation was to high during input voltage oscillation.

    Too high? Please provide exact data so we see what you are talking about.

    Raja sekaran said:
    Can you please explain is ADC reference will varry with respect to input oscillation (~20 to 60 mV of input oscillation)

    Usually source of noise is not reference - if properly used :)

  • 0 in reply to Ilmars
    Guru 227245 points

    Often, ripple current on the ground traces is lifting the GND reference level, and results in reading variations, even if the internal reference is stable, relative to MSP GND. That’s why some MSPs have a separate AVSS pin which should NOT be connected to DVSS directly, but should be routed separately to the supply GND pin. All analog parts should use this same AVSS signal as GND reference and shouldn’t inject any currents into it.

    Being a band gap reference, the internal MSP reference is quite stable regarding changes in VCC. It is, however, stable against its internal VSS, not against what you may decide to pick as GND level somewhere else on the PCB.

  • 0 in reply to Jens-Michael Gross
    Guru 74080 points

    Hey Jens,

    connecting AVSS to DVCC, directly or indirectly, is never a good idea, I think :-)

    ...don't blame me, just meant as joke...

  • 0 in reply to Dennis Eichmann
    Guru 227245 points

    Dennis Eichmann said:
    connecting AVSS to DVCC, directly or indirectly, is never a good idea, I think :-)

    Of course you’re right. I’ve corrected the typo.

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