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MSP430F477: External Vref max

BO
Genius 12760 points
Part Number: MSP430F477

Can you clarify what the maximum external Vref voltage is for the device? The spec shows max Vref=AVcc+0.2V in the DAC section and another value listed in the ADC section states max Vref=1.5V.

Regards Bernd

  • 0
    TI__Mastermind 49692 points

    Hello Bernd,

    As you've observed, the maximum external reference voltage depends on the specific module you're wanting to use. Let's assume you're using the DAC but not the ADC, and the Vref voltage is AVCC + 0.2V. This will be fine since you're not enabling the ADC module. I hope this makes sense.

    Regards,

    James

  • 0 in reply to James Evans
    TI__Prodigy 90 points

    Hi James,

    From your response I believe the Vref on the DAC and Vref on the ADC are separate circuits. The DAC Vref is derived from the AVcc input and not the Vref (Pin 60). Is this correct?
    The recommended external Vref for the ADC is half scale of the AVcc input voltage to the uC. If AVcc is 2.8V then the max input to Vref (Pin 60) is 1.4V. Is this correct?
    I've found a circuit in our library that has the external Vref at 3.0V (Pin 60) on the MSP430F477. I want to make sure the device is not overstressed. This design uses both the DAC and ADC circuits.

    Daniel (supporting Jamie)

  • 0 in reply to Daniel Studer
    TI__Mastermind 49692 points

    Hi Jamie,

    Daniel Studer said:
    From your response I believe the Vref on the DAC and Vref on the ADC are separate circuits. The DAC Vref is derived from the AVcc input and not the Vref (Pin 60). Is this correct?

    It depens on how you configure the reference for the DAC. As you can see from the user's guide, the DAC can use either AVCC as the reference, the 1.2 V reference from the SD16 ADC module or an external reference. Keep in mind that this is different than the 1.5 V or 2.5 V voltage reference in the ADC12 module.

    Daniel Studer said:
    The recommended external Vref for the ADC is half scale of the AVcc input voltage to the uC. If AVcc is 2.8V then the max input to Vref (Pin 60) is 1.4V. Is this correct?

    Which ADC are you referring to? ADC12 or SD16? This information should be provided in the datasheet and/or user's guide.

    Regards,

    James

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