• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 82 subscribers
  • Views 377 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F28379D: Use of ramp generator in analog comparator module

Bisnupad .L
Prodigy 20 points
Part Number: TMS320F28379D
Other Parts Discussed in Thread: TIDM-DC-DC-BUCK

Hi Experts,

I am trying to implement the ramp generator feature available in analog comparator module of F28379D mcu for implementation of peak current mode control (as shown below).

I am unable to get clear information on the following aspects,

In TMS320F2837xD Dual-Core Microcontrollers Technical Reference Manual (spruhm8i, page-1773), it has been mentioned that the ramp generator produces a falling-ramp input for the high reference 12-bit DAC. The reference 12-bit DAC uses the most significant 12 bits of the RAMPSTS countdown register as its input. On setting DACSOURCE = 1, the value of RAMPSTS is loaded from RAMPMAXREFS. My doubt is as the RAMPMAXREFS is a 16-bit register, the output of voltage loop pid controller will give a value corresponding to 12-bit register as ADC of voltage sensor is 12 bit. Do I need to converter the 12-bit value (range 0-4095) of ic into 16-bit value (range 0-65535) and also is this changed value will be assigned to RAMPMAXREFS?

How to choose the value of RAMPDECVAL?

The low 4 bits of the RAMPSTS countdown register effectively act as a prescale for the falling -ramp rate configurable with RAMPDECVALA. How this concept works?

Experts please share your valuable suggestions in the above quires?

Note:  I have referred to the documents like TIDM-DC-DC-BUCK, Digital Peak Current Mode Control with Slope Compensation Using the TMS320F2803x and spruhm8i, but not able to get proper answer to my doubts.

  • 0
    TI__Intellectual 1200 points

    Hi, 

    Please find the response below:

    1.Do I need to converter the 12-bit value (range 0-4095) of ic into 16-bit value (range 0-65535) and also is this changed value will be assigned to RAMPMAXREFS?

    No, you don't need to convert.

    2.How to choose the value of RAMPDECVAL?

    It determined by your power circuit to avoid sub-harmonic oscillation. Please refer to the classic PCMC papers.

    3.The low 4 bits of the RAMPSTS countdown register effectively act as a prescale for the falling -ramp rate configurable with RAMPDECVALA. How this concept works?

    You can neglect the last 4 bits. The the 12-bit DAC will only take the most significant 12-bit of the RAMPSTS countdown register as input.

    Thanks,

    Qing