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Original question:

F28377D ADC and Comparator

TMS320F28377D: Comparator subsytem CMPSS hardware configuration

Sapna R
Prodigy 30 points
Part Number: TMS320F28377D

I have a few basic questions relating to the Comparator subsystem module of TMS320F28377D.

 I am trying to compare a +/-10 V signal with another analog signal by giving the signals to CMPIN1P and CMPIN1N respectively.Based on the comparartor result, say, I would like to block the PWM .

1) As +/- 10V signal cannot be given directly to the DSP, should I do a voltage level shifting to 3.3V or below?

2) Can we give bipolar signals directly as inputs to CMPIN1P and CMPIN1N, or use hardware to convert it to unipolar?

3)Comparator subsystem 1 consists of two comparators- top and bottom one. Lets say, we give +/-10V signal to CMPIN1P and another analog signal at CMPIN1N. In this case, won't CTRIP1H and CTRIP1L be the same?Also, won't CTRIPOUT1H and CTRIPOUT1L be the same?

Thanks,

  Sapna

  • 0
    TI__Mastermind 28275 points

    Hi Sapna,

    Answers to your questions below:

    1) That's right. You can't supply 10V to the MCU, you'll damage it. You should level shift it. You can also just use a voltage divider.

    2) F28377D is a single supply MCU so it can't accept bipolar signals. Yes, you will have to convert it to unipolar.

    3) That's right. On F28377D, if you apply a signal to both CMPINxP and CMPINxN, provided the COMPDAC isn't used, you'll get the same output on CTRIPxH/L and CTRIPOUTxH/L.