TMS320F28377S: inquiry about EPWM behavior

robin Moon

Part Number: TMS320F28377S

Tool/software:

My customer is using TMS320F28377S and has inquiries about EPWM behavior.

currently, EPWM configuration is as follows:

SYSCLK : 200MHz
EPWM CLK : 100MHz
CTRMODE : Up/down count
SHDWAMODE : Shadow mode
LOADAMODE : Zero
AQCTLA.bit.CAU : AQ_CLEAR
AQCTLA.bit.CAD : AQ_SET

Q1. When the compare register(CMPx) is in shadow mode, what happens to the PWM signal if the Shadow-to-Active load time and Timer counter register value and compare register value have the same?

Q2. How long does it take for the AQCTL register to clear the signal?

thanks

B.R,

7 months ago

0 Allison Nguyen 7 months ago

TI__Mastermind 23960 points

Hi Robin,

The TRM description recommends that if loading on zero, CMPx values be greater than 0 for this reason:

Best Regards,

Allison

0 robin Moon 7 months ago in reply to Allison Nguyen

Expert 1520 points

Hi Allison

I have additional question.

My customer's project is an industrial inverter.

there is a full turn on section and a full turn off section in the inverter topology,

if CMPA/CMPB are used as the minimum(1), it will not be fully turned off.

Please let me know how I can switch the full turn on section to full turn off section completely without switching loss.

thanks

B.R,

0 Allison Nguyen 7 months ago in reply to robin Moon

TI__Mastermind 23960 points

Hello Robin,

We have an app note explaining how to have full 0 to 100% duty cycle EPWM that can be referenced:

https://www.ti.com/lit/an/spraai1/spraai1.pdf

Best Regards,

Allison

0 robin Moon 7 months ago in reply to Allison Nguyen

Expert 1520 points

Hi Allison

Thanks for prompt feedback.

They are trying to follow the guide you provided.

in case of the PWM period and the ISR period are different, is it possible to allow your guide?

thanks

B.R

0 Delaney Woodward 7 months ago in reply to robin Moon

TI__Mastermind 20490 points

Hi Robin,

Allison is currently out of office but will have a response back to your question when she returns later this week.

Best Regards,

Delaney

0 Allison Nguyen 7 months ago in reply to robin Moon

TI__Mastermind 23960 points

Hi B.R.,

Thanks for your patience. Differing PWM and ISR period should be fine if you are loading your updated variables accordingly. What are the load settings for those parameters, and where are you updating the values (other ISR, CLA task, etc)? What is the frequency of PWM and frequency of update?

Best Regards,

Allison

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TMS320F28377S: inquiry about EPWM behavior