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TMS320F28374S: Questions for TMS320F28374s ADC peripheral

Benjamin Zhou
Expert 4000 points

Part Number: TMS320F28374S

Hi Team,

  My customer reported an issue while using ADCIN14/ADCIN15 for sampling, that while configure the ADCIN14&ADCIN15 to all the 4 ADC modules,  while the ADCIN14/ADCIN15 input voltage is <-0.4v,  all the ADC results of the ADC inputs will drop to 0.   while configure the ADCIN14 & ADCIN15  to single ADC module,  while the ADCIN14/ADCIN15 configure to single ADC module,  the negative voltage(<-0.4V) will not affect to the other ADC input of configured ADC module.

  Could you kindly give comments why this situation happened,  and how to avoid the situation while configure the ADCIN14 & ADCIN15 to all the ADC modules.?

  • 0
    TI__Guru 60865 points
    Hi Benjamin,

    When the voltage is below -0.4V, what is the current into the pin?; Is the current limited enough to ensure there is no damage to the device?

    In general, when exceeding the device absolute maximum ratings we are worried about whether the device will be damaged or not; correct operation is not expected.

    Is the behavior any different on pins dedicated to a specific ADC? e.g. if ADCA3 has a voltage less than the device absolute max applied to it and ADCA3 is sampled do other channels on ADC-A read 0?
  • 0 in reply to Devin Cottier
    TI__Expert 4000 points
    Hi,
    The current of ADC Pin would be limited to less than 1mA; what's your suggestion of the current limitation?
    It's quite different for the other specific ADC pin compared to ADCIN14 & ADCIN15. e.g. if ADCAIN3 has input less than -0.4V, the ADC result of ADCIN3 is 0, and the other ADC pin of ADCA module would be no affected, customer has verified that of all of other ADC input pin for specific ADC module that the negative voltage would not affect other ADC input samples.
    And what's the difference for ADCIN14 & ADCIN15 compared to other ADC input pins? Why only the 2 ADC inputs would have such situation? and what's your suggestion for the ADCIN14&ADCIN15 usage?
    Expect for your reply, thanks.

    Best Regards
    Benjamin
  • 0 in reply to Benjamin Zhou
    TI__Guru 60865 points
    Hi Benjamin,

    As long as not every channel is experiencing -0.4V and 1mA at the same time, this should be OK.

    The main difference for these channels is that they fan-out to every ADC. Can you confirm that you don't see the same effect on channel A0/A12/B12/C12/D12, which also fans-out to all 4 ADCs?

    Has the customer observed this behavior on more than 1 device?
  • 0 in reply to Devin Cottier
    TI__Expert 4000 points
    Hi Devin,
    Very appreciated, Customer is working on clarifying the other ADC inputs behavior, and would let you know the updates.

    Best Regards
    Benjamin
  • 0 in reply to Benjamin Zhou
    TI__Guru 60865 points
    Hi Benjamin,

    Any update on customer check of A0/A12/B12/C12/D12 performance vs ACIN14/15?