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CCS/TMS320F28377D: Issues with ADC PPB pulse timing

Zach Warres
Prodigy 10 points
Part Number: TMS320F28377D

Tool/software: Code Composer Studio

I'm trying to get an ADC PPB HI trip to trip a PWM. I have 12 ADCs set in continuous mode that go through a PPB, to the XBAR, and then trip the PWMs. However, this only works some of the time. My suspicion is that the pulse coming out of the ADC Post processing block is not long enough to always trigger the PWM trip. I tested this by changing the ADC start of conversion trigger to a slower software pulse instead of leaving the ADCs in continuous mode. In this condition, the trip logic always works. It appears as though, the ADCs, while in continuous mode, are unable to reliably send a long enough pulse out to the PWM. Is there a way around this? I would use the CMPSS functionality, but it doesn't look like I can tie 12 CMPSS inputs to the chip.

Thanks,

Zach

  • 0
    TI__Guru 57255 points

    Hi Zach,

    Please take a look at the 'ADC PPB Event Trigger (ADCxEVT) to ePWM Digital Compare Submodule' Advisory within this device's errata.  This advisory should not affect RevC silicon.

    If your various trip values at the C2000 device-side (0-3.3V) are not all near each other, it is possible to utilize each CMPSS's comparator (the high & low comparator) for a total of 16 (8*2) comparators.  These can then come into the EPWMXBAR, get OR'd together, and then get into the ePWM peripheral.  If you utilize both comparators per CMPSS, as I've described, please be aware of the 'CMPSS DAC output disturbance' specification in the datasheet.


    Thank you,
    Brett