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TMS320F280034: VREFHI use as external offset

Joyce Gao
Expert 3200 points

Part Number: TMS320F280034

Hi expert,

Customer wants to use VREFHI as external offset for current sampling circuit and through test it seems OK. Are there any risks to do this and is it a common use case? Or, could you help give some advice for using it safely as external offset? Is there any app note related with this? Thanks!

Joyce 

  • 0
    TI__Genius 11081 points

    Hello Joyce,

    The key thing to keep in mind with VREFHI is that better your reference voltage is regulated, the less dynamic error is introduced into your ADC conversions. If your external offfset input is very high impedance and not expected to create a current load on the reference, then you're probably OK. Otherwise, any kind of load on the reference potentially impacts its ability to respond to the fast current pulses that are generated by the SAR ADC circuits. You might be able to counter this effect to some extent by increasing capacitor size on the pin.

    Overall, I would not recommend doing this unless:

    • The external offset input is very high impedance, or
    • You're using an op amp buffer with the bandwidth to negate any current loading effects.

    Best regards,
    Ibukun