I'm using F28335 ePWM complementary deadband, but I'm seeing A/B output overlap!

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Submitted by schaefr on Mon, 06/29/2009 - 22:42 

I am using a 28335 eZdsp. I need to produce two pwm signals, one of which is the inversion of the other with deadband. When I test the following program and look at the pwm signals that are being produced, one of the pwm signals is sometimes high when the other is high despite using active high complimentary with deadband. Have I set up the pwm incorrectly or is there some other problem with my program that is causing this problem?

Thanks, Robert Schaeffel

Tagged:

Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited November 2020

    Submitted by pete on Mon, 06/29/2009 - 22:47.

    Hi Robert,
    Yes, you are seeing overlap in your debug monitor buffers. The problem is that you didn't sync the monitor buffer trigger to fire only when both buffers were empty. This can cause one buffer to fill on one sync pulse and the other buffer to fill on a different pulse giving time skewed wave forms that don't appear complementary. The enclosed diagram has been changed to sync both buffers and allow a sweep of duty cycle with a slider and observe both A&B PWM waveforms. It also sums the two PWM vectors and plots the sum to make it easy to spot a case of both PWMs active. You will see that they never are.
    These diagrams were compiled for an F2808 so you will need to select F28335 as target in DSP Config... and recompile.
    Regards, Pete

    Unable to find an attachment - read this blog

Categories