TMS320F28375D: About HRPWM (CMPAHR and CMPBHR)

O.H

Part Number: TMS320F28375D

Tool/software:

Hi experts,

Q:When controlling the duty ratio precisely with the HRPWM of the TMS320F28375D, do CMPAHR and CMPBHR always need to be the same value?

Currently, my customer is using HRPWM to control the PWM duty ratio at any frequency.
If the values of CMPAHR and CMPBHR are different under certain frequency conditions, jitter of about 10ns (1 count) occurs at the rise of the PWM pulse.
Setting CMPAHR and CMPBHR to the same value is effective in suppressing jitter, but this method does not achieve the desired duty control.

Best regards,
O.H

6 months ago

0 Stevan Duraskovic 6 months ago

TI__Expert 4690 points

Hello,

Please refer to the device TRM, section 15.14.1.5.3 Duty Cycle Range Limitation: https://www.ti.com/lit/ug/spruhm8k/spruhm8k.pdf for more clarification.

CMPAHR and/or CMPBHR would experience jitter if they are under 3 TBCLK or TBRD - 3 TBCLK.

0 O.H 6 months ago in reply to Stevan Duraskovic

Mastermind 6660 points

Hello,

Thank you for your reply.

O.H said:
Q:When controlling the duty ratio precisely with the HRPWM of the TMS320F28375D, do CMPAHR and CMPBHR always need to be the same value?

In other words, regarding the above question, is it correct to understand that "No, they don't have to be the same"?

Best regards,
O.H

+1 Stevan Duraskovic 6 months ago in reply to O.H

TI__Expert 4690 points

Yes, correct. They do not have to be the sane. However, keep in mind that for HRPMW application CMPAHR is used to configure duty for EPWMA output, and CMPBHR for EPWMB output. You cannot use CMPAHR and CMPBHR to configure EPMWA output.

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TMS320F28375D: About HRPWM (CMPAHR and CMPBHR)