• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 83 subscribers
  • Views 292 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TMS320F280039C: Clarification discrepancy in CMPSS Trip Function Performance Between LAUNCHXL-F280039C and F280039C Control Card

Prathamesh Jadhav
Prodigy 30 points
Part Number: TMS320F280039C
Other Parts Discussed in Thread: LAUNCHXL-F280039C, , TIDM-DC-DC-BUCK

Tool/software:

Hello,

We are working with the TMS320F280039C MCU and using the CMPSS trip function to disable the PWM in the event of an overcurrent. We have both the 'LAUNCHXL-F280039C' and the 'F280039C control card'. The code works perfectly on the Launchpad but shows deviations from the actual tripping set point on the control card. Currently, we are unsure why the trip event produced by the same F280039C on the Launchpad differs from that on the control card. We are using the 'TIDM-DC-DC-BUCK' firmware as the base code for the TMS320F280039C microcontroller.

Thanks & Regards,

Prathamesh.

  • +1
    TI__Expert 4690 points

    Hello,

    It is possible that different devices have some small deviation in accuracy level. There is a note from F280039C data sheet about input referred offset and hysterisis: "The CMPSS inputs must be kept below VDDA + 0.3 V to ensure proper functional operation.....The comparator could begin to output an incorrect result depending on the value of the other comparator input." 

    Calibrating the CMPSS module could fix the issue with getting wrong CMPSS values, Input referred offset error / Static offset error. More information on this can be found in device TRM: https://www.ti.com/lit/ug/spruiw9c/spruiw9c.pdf, Chapter 18.6.3. Calibrating the CMPSS.

    Since you are using TIDM-DC-DC-BUCK design, I see that it is using digital filter option by default. Filtering can slow it down, so changing the Prescale, Sample Window, and Threshold values could improve the accuracy. 

  • 0 in reply to Stevan Duraskovic
    Prodigy 30 points

    Hello Stevan,

    You are correct. Due to my hardware configuration, I was getting a voltage greater than (VDDA + 0.3V) at the CMPSS inputs, which caused a discrepancy in the CMPSS trip function.

    I appreciate your timely reply

    Thanks & Regards,

    Prathamesh Jadhav.

  • 0 in reply to Prathamesh Jadhav
    TI__Expert 4690 points

    Glad I could help. Have a nice day!