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TMS320F280049C: Minimum decrement value of ramp generator and related application

Johnny Chen
Expert 4450 points
Part Number: TMS320F280049C

Hi Champ,

I am asking of after receiving the selected EPWMSYNCPER signal, the value of RAMPDECVALA is subtracted from RAMPSTS which is loaded from RAMPMAXREFS on every subsequent SYSCLK cycle.

With using the ramp generator, it is known that the minimum decrement value is 1 which is set in the RAMPDECVALA register.

So, if it converts to actual output voltage, the minumim decrement voltage is calcualted with 1*3.3(DACREF)/4096.

If the slope compensation requires for decrement voltage is smaller than this value(1*3.3/4096), is it possible to implement by hardware only?

The only way I can think of is to reduce the interval in every step, however it needs to pull up the frequency much higher since the action executing after receiving EPWMSYNCPER signal.

Is there any other workarounds to achieve the application without pulling up the frequency ?

I think my understanding of the usage of ramp generator is correct, please correct me if there is wrong.

Thanks for any suggesttion and correction.

Best Regard,

Johnny

  • +1
    TI__Mastermind 28275 points

    Hi Johnny,

    Output voltage wise, the minimum decrement value of the compdac is still 1LSB i.e 3.3/4096. RAMPDECVALS<16 effectively act as a prescale because RAMPSTS is 16-bits and the compdac uses the MSB 12-bits of RAMPSTS.

    For example:

    1. RAMPDECVAL of 8 will lead to a 1LSB change in compdac value every 2 sysclks.

    2. RAMPDECVAL of 16 will lead to a 1LSB change in compdac value every 1 sysclk.

    3. RAMPDECVAL of 32 will lead to a 2LSB change in compdac value every 1 sysclk.

    etc.

    Not sure if this answers your question but let us know if it's not clear.