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Original question:

TMS320F28027: angle compensation

TMS320F28027: adc clock

zhou qicheng
Intellectual 790 points
Part Number: TMS320F28027
Other Parts Discussed in Thread: MOTORWARE

Tool/software:

Hello, D:\ti\motorware\motorware_1_01_00_18\sw\solutions\instaspin_foc\boards\boostxldrv8305_revA\f28x\f2802xF\projects\ccs\proj_lab10a Using official examples, it is found that The adc clock says that the adc clock is 45mhz at the maximum, so it is divided by two.

But I read the manual, and the adc can reach 60mhz at most.

I tried dividing by two and not dividing by two, and both can be used normally, but the phase current collected by dividing by two will get worse at high motor speed. Can I use 60mhz for adc?

  • 0
    TI__Mastermind 36526 points

    Hi,

    zhou qicheng said:
    I tried dividing by two and not dividing by two, and both can be used normally, but the phase current collected by dividing by two will get worse at high motor speed. Can I use 60mhz for adc?

    Could you please see the errata for this MCU? The linearity will be very poor at 60MHz and will not meet datasheet specifications. The errata lists the specifications for INL and DNL at 60MHz. 

    We generally recommend 30MHz ADC clock for best performance. 

    Best Regards,

    Ben Collier

  • 0 in reply to Benjamin Collier
    Intellectual 790 points

    Hello,
    I found that switching the sampling order between phase B and phase C resulted in a decrease in the quality of the previously good phase B sampling, which was similar to the waveform of phase C, while the previously poor phase C sampling improved. I suspect this may be caused by the sampling time. How can I solve this problem,
    2， ADC_setSampleOverlapMode Is this a multiple sampling? Is it related to ADC clock? Can it be closed?

  • 0 in reply to zhou qicheng
    TI__Mastermind 36526 points

    Hi,

    I think you should take a look at this app note, this sounds like cross talk: https://www.ti.com/lit/pdf/spracw9

    zhou qicheng said:
    Is it related to ADC clock? Can it be closed?

    I'm not sure what you mean by this? It is possible to sample two channels at the same time, and then convert them sequentially. You are able to choose this, or you can sample + convert sequentially.

    Best Regards,

    Ben Collier