TMS320F28034: 0-100% Duty cycle

Marvn Arcangel

Hi Team,

Can you please check the inquiry below?

I would like to confirm if this device can achieve a 0-100% duty cycle.

For type 1 epwm module duty cycle from 0~100% can be achieved by setting ZRO bit and PRD bit for that epwm because 28034 has a type 1 epwm module,so a 0~100% duty cycle can be achieved simply by setting ZRO and PRD bit of AQCTLA register.

As an example, settting AQCTLA a full range duty cycle can be achieved like bellow：

EPwm2Regs.AQCTLA.bit.ZRO = 0x1; // Set: force EPWMxA output low
EPwm2Regs.AQCTLA.bit.PRD = 0x2; // Clear: force EPWMxA output high
EPwm2Regs.AQCTLA.bit.CAU = 0x2; // Set: force EPWMxA output high
EPwm2Regs.AQCTLA.bit.CAD = 0x1; // Clear: force EPWMxA output low

After setting as above,epwm2 can output 0~100% duty cycle.

Would you kindly confirm?

Regards,

Marvin

over 3 years ago

0 Marlyn Rosales Castaneda20 over 3 years ago

TI__Mastermind 27110 points

Hi Marvin,

Marvn Arcangel said:
As an example, settting AQCTLA a full range duty cycle can be achieved like bellow

Can you please re-attach the figure? The settings described for AQCTLA are difficult to interpret without it.

In general though, 0-100% duty is achievable on this device. The way you achieve this is by changing the value of CMPA and or CMPB (compare values), not through the action qualifier settings. The 'Waveforms for Common Configurations' section of the TRM within the EPWM chapter has more details on this topic.

Best Regards,

Marlyn

0 Marvn Arcangel over 3 years ago in reply to Marlyn Rosales Castaneda20

TI__Genius 16530 points

Hi Marlyn,

Good day.

The customer read the technical reference and is still not clear about it. Here is the response:

"According to the pdf (in page 257),If you load CMPA/CMPB on zero, then use CMPA/CMPB values greater than or equal to 1. If you load CMPA/CMPB on period, then use CMPA/CMPB values less than or equal to TBPRD-1.So I can't achieve a 0~100% duty cycle just by change CMPA or CMPB.

As the possible full range duty cycle I mentioned in the previous mail,duty cycle change is also made by changing CMPA or CMPB from zero to TBPRD.I just forgot to say that.The diffrence is that by setting ZRO and PRD bit of AQCTLA,CMPA or CMPB can be set any value from zero to TBPRD and will take effect when loaded.This makes it possible to achieve 0~100% duty cycle."

The customer claimed that there is a TI doc that explains this (but can't remember which). I also can find the document they are referring to.

Can you help clarify?

Thank you.

Regards,

Marvin

0 Marlyn Rosales Castaneda20 over 3 years ago in reply to Marvn Arcangel

TI__Mastermind 27110 points

Hi Marvin,

Marvn Arcangel said:
"According to the pdf (in page 257),If you load CMPA/CMPB on zero, then use CMPA/CMPB values greater than or equal to 1. If you load CMPA/CMPB on period, then use CMPA/CMPB values less than or equal to TBPRD-1.So I can't achieve a 0~100% duty cycle just by change CMPA or CMPB.

Is the customer planning on using up-down count mode?

This is the document that explains 0-100% duty for EPWM Type-0: www.ti.com/.../spraai1.pdf

For devices with EPWM Type >0, the workaround for up-down count still needs to be applied. The following threads provide more context

Best Regards,

Marlyn

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F28034: 0-100% Duty cycle