TMS320F28033: Wrong output EPWM frequency

Chen Yang

Part Number: TMS320F28033

Hi team,

My customer use F28033 in their LLC power supply.

They set the software frequency limit to 70kHz, but in some special situation the real EPWM output frequency is lower 70kHz to minmax 50kHz.

Customer want to identify the reason cause this issue, Is there a possibility that the DSP clock is abnormal due to the interference of the external crystal oscillator?

They want to grab GPIO18 (XCLKOUT) while grabbing the abnormal operating frequency to verify whether the abnormal wave is caused by the abnormal SYSCLK. Is this method feasible?

What's your advices in this case?

Looking forward to your reply!

Thank you so much!

over 2 years ago

0 Krishna Allam over 2 years ago

TI__Expert 7985 points

Hi Chen, Thanks for reaching out. Please expect a delay in reply due the long weekend in observance of Dr. Martin Luther King day. Regards, Krishna

0 Cody Watkins over 2 years ago

TI__Mastermind 41315 points

Chen Yang said:
Customer want to identify the reason cause this issue, Is there a possibility that the DSP clock is abnormal due to the interference of the external crystal oscillator?

Yes this is possible, but there are other possibilities as well.

Chen Yang said:
They want to grab GPIO18 (XCLKOUT) while grabbing the abnormal operating frequency to verify whether the abnormal wave is caused by the abnormal SYSCLK. Is this method feasible?

The customer's system will determine if this type of debug is feasible. From the C2000's perspective this is a very basic debug function intended for use cases such as this.

If the XCLKOUT pulse train looks normal then I would check the PWM settings. What frequency is before and after the abnormal condition?

Is the sync chain being used? Is TBPHS being used? what actions are being used in the AQ module, is SET, CLEAR, or TOGGLE being used?

Regards,
Cody