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TMS320F280049: VREFHI input current

HS FAE Germany
Mastermind 32440 points
Part Number: TMS320F280049


Hi,
I have a question to the VREFHI input current in the datasheet (7.10.1.2.2 ADC Characteristics, page 104). Is this for the complete ADC or do I have to multiply it for each VREF input: VREFHIA, VREFHIB, VREFHIC?

Regards, Holger

  • 0
    TI__Guru 50611 points

    Hi,

    Due to Thanksgiving Holiday, the subject matter expert is out of office. We will get back to you next week.

    Thanks & Regards,
    Santosh

  • 0
    TI__Genius 11081 points

    Holger,

    This applies for each ADC module you are using. So, if you are going to be performing conversions on 3 ADCs synchronously/at the same time, then yes it would apply for each of the VREFHI inputs; so assuming you have one driver driving all 3 pins, the total current load would be 3x.

    One thing I will point out here though is that the number specified in the datasheet is a typical number and does not represent the peak. ADC conversions trigger a series of very short transient current pulses/spikes on the VREFHI pin, which can be higher, up to ~150uA. In designing your reference driver circuit, transient response/load regulation is much more critical, and this is why we generally recommend using an op amp buffer on VREFHI to get the best ADC performance.

  • 0 in reply to Ibukun Olumuyiwa
    TI__Mastermind 32440 points

    Hello Ibukun,
    thanks for your reply. May be this should be added to the datasheet that it is the input current for each VREFHI input.

    Regards, Holger

  • 0 in reply to HS FAE Germany
    TI__Mastermind 32440 points

    so one additional comment, do you mean that the peak current is 150uA? So average current 130uA+150uA per ADC?

  • 0 in reply to HS FAE Germany
    TI__Genius 11081 points

    Hello Holger,

    The ADC conversions result in a series of current load spikes on VREFHI of varying magnitude. The maximum/peak of these transient spikes is in the neighborhood of 150uA for the F28004x ADC. The "typical" number in the datasheet is the average current draw.