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MSPM0L1306: epwm output resolution

Johnny Chen
Expert 5060 points
Part Number: MSPM0L1306


Hi Champ,

I am asking for my customer.

In previous design, customer is using competitor's MCU to have pwm control controlling the power stage.

Due to the poor epwm output resolution from competitor (10-bit), customer is evaluating M0 solution which has integrated 16-bit timers.

What my customer wants to know, as a 16-bit timer for generating epwm signal, what is the resolution rating (i.e. the decimal place for pwm duty (50%,50.X%, 50.XX%?)) we could achieve ? 

Is there a way to know the formula showing the conversion from digit to analog output signal is done ?

Thanks and regards,

Johnny

  • 0
    Guru 42195 points

    Well, a back of the envelope calculation shows that if you set TIMG0 to the max PWM Period count of 65535, the values range from 0 for 100 % duty cycle to 32767 for a 0% duty cycle for a range of 32767 counts. Each count would be roughly a change of .003 %

  • +1
    TI__Mastermind 29105 points

    Hey Johnny,

    As Keith mentioned, a 10bit timer has a max resolution of 2^10 = 1024 steps. and so 100% / 1024 = ~ .1% accuracy.

    a 16 bit timer has max resolution of 2^16 = 65535 steps and so 100% / 65535 = ~.0015% accuracy.     

    Also, the clock speed and period of the timers is also important.  At very high speeds where using the entire timer period isn't possible, then the accuracy of both may drop a bit.   

    For your question about "Formula showing conversion from digit to analog output signal" - Is the customer trying to do a PWM to analog output?  Sometimes this is called a "Digital DAC"?    This is harder to quantify but generally, a higher resolution timer is going to give a finer output but again, speed and filter configuration are important.  Here is an app note on very high performance PWM DACs.  https://www.ti.com/lit/an/slyt795/slyt795.pdf?ts=1708985241062&ref_url=https%253A%252F%252Fwww.google.com%252F 

    Also to note on the M0L1306, it is possible to route the internal 8-bit DAC out of the OPA and on MSPM0Gxx devices there is an integrated 12-bit DAC that is externally exposed.

    Thanks,

    JD