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which kind of current sampling method would be better?

Eric Ma
Intellectual 2630 points

Hi  C2000 App team

My customer used F28376S for their servo control develop. They asked for TI suggestion about current sampling.

The PWM period is 62.5us in updown mode, CMPA registers are modified in counter == period, and they used hall current sensor or AMC1305 with SINC for current sampling.

The question is: which kind of SOC trigger can get better result servo control?  single trigger or oversampling?

Eric

  • TI__Mastermind 43730 points
    Eric,

    Very tough question to answer, it all depends on where the bottle neck is in the system

    If they have issue with phase delay, oversampling may not be good. And if they want to reduce noise oversampling helps.

    For SDFM AMC1305, more oversampling will not help, note SDFM itself is an oversampled A/D converter that runs at 20Mhz.

    If they use hall current sensor because the ADC is fast, they can map the Il1-IL3 to three different A/D converter and do oversampling.

    Where they trigger the sample is another question. Typical points are ZRO and Period, some servo customer may use dual update to improve BW in the system as well in which case the trigger will be ZRO and PRD
  • in reply to Manish Bhardwaj
    TI__Intellectual 2630 points

    Hi Manish

    Thanks for your comments.

    "If they use hall current sensor because the ADC is fast, they can map the Il1-IL3 to three different A/D converter and do oversampling."

    For above comments, you mean map IA, IB, IC to F2837x three different ADCs and do oversampling, corrents? In this condition, what is your suggestion to set the trigger SOC?

    For the dual update in servo, that also mean update duty CMPA in ZRO and PRD?

    Eric