• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 30 subscribers
  • Views 101 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.

Original question:

MCT8329A: If I want to control the speed for an external command, how should I set the "REF_PROFILESx" register?

MCT8329A: REF_OFF2 and DUTY_OFF2 Settings in MCT8329A Linear Mode

Conor
Guru 12235 points
Part Number: MCT8329A

Tool/software:

Hi,

I am currently using the MCT8329A in Linear Mode (REF_PROFILE_CONFIG = 0x01) to implement speed control according to the following conditions:

  • 10% to 90% duty cycle → Speed varies from 8000rpm to 66000rpm (linear control).
  • Above 90% duty cycle → Speed is fixed at 66000rpm.

I have set REF_OFF2 = 66000rpm instead of 0rpm, but I observed that changing this value does not affect the operation (i.e., whether set to 0x00 (0rpm) or 0xFF (66000rpm), the motor behavior remains unchanged).

Questions & Concerns:

  1. Is it correct to set REF_OFF2 to 66000rpm instead of 0rpm in this configuration?

    • Given that REF_OFF2 applies when DUTY_CMD ≤ DUTY_OFF2, could it be that my current settings prevent REF_OFF2 from being applied?

  2. Current settings for DUTY_ON2 and DUTY_OFF2:

    • DUTY_ON2 = 90%
    • DUTY_OFF2 = 100%
    • REF_OFF2 = 66000rpm
    • REF_CLAMP2 = 66000rpm

    Issue: Since DUTY_OFF2 is set to 100%, it might not be functioning as expected. Should DUTY_OFF2 be set to a lower value (e.g., 85%) to introduce hysteresis and allow REF_OFF2 to take effect?

  3. Recommended Configuration:

    • If the goal is for the motor to stop when the duty cycle is below 10%, while maintaining stable operation between 10% and 90%, is the following setting correct?
      • DUTY_OFF2 = 85%
      • DUTY_ON2 = 90%
      • Also, what value should be set for REF_OFF2?

I would appreciate your confirmation on whether REF_OFF2 should be set to 0rpm and whether DUTY_OFF2 should be lowered to allow proper hysteresis.

Best regards,

Conor

  • 0
    TI__Expert 6011 points

    Hello Conor,

    1. Ideally setting REF_OFF2 to 66000rpm should have worked in your case. Not sure what is going wrong, let me confirm with my own experiments once.

    2. Here, Set DUTY_OFF2 > DUTY_ON2. And if you are sure that the duty won't exceed 90%, you could maybe set DUTY_OFF2 to 95% and DUTY_ON2 to 85%-90%. So that till 90% the motor is clamped to REF_CLAMP2 = 66000rpm. 

    Conor said:
    If the goal is for the motor to stop when the duty cycle is below 10%, while maintaining stable operation between 10% and 90%, is the following setting correct?
    • DUTY_OFF2 = 85%
    • DUTY_ON2 = 90%
    • Also, what value should be set for REF_OFF2?

    Thanks and regards,

    Sachin S