• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 30 subscribers
  • Views 332 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.

MCF8316A: How do you disable the MPET?

David Gustavson1
Prodigy 210 points
Part Number: MCF8316A

The motor seems to go through the motor parameter test sequence before running.  So it speeds up for a few seconds, stops, then starts running again.  I don't want it to do this in the target system.  Once the correct parameters are programmed into the EEPROM, I just want the motor to start running when power is applied to the chip. 

  • 0
    TI__Expert 5578 points

    Hi David,

    Thanks for your question on the Motor Drives E2E forum.

    For a better understanding of how the MPET routine works on this device I can suggest going through section 7.3.13 Motor Parameter Extraction Tool- (MPET) of the datasheet, see below:

    Short answer: As long as the MPET sequence conditions are FALSE for all four steps, MPET will essentially be skipped:

    You can see those conditions listed under each step of Figure 7-37:

    For example, for some of the steps you may need to make sure to set MPET_R, MPET_L, and MPET_KE to 0h as seen below:

    Best,

    Robert

  • 0 in reply to Robert Wedan
    Prodigy 210 points

    Thanks, Robert.  I am at a loss as to what to set SPD_LOOP_KI and KP to.  If I let the MEPT run, then read the registers and check register 0xF2, I see that SPEED_LOOP_KI has been updated from 0x000 to 0x0D5.  However, SPEED_LOOP_KP is still 0x00.  If I leave it like this, the MPET will still run on power up, correct?  Should I just set it to 0x001?

  • 0 in reply to David Gustavson1
    TI__Expert 5578 points

    Hi Dave,

    Ultimately you will want to optimize Kp and Ki for your solution to meet your key care abouts and certain project requirements. This Tuning Guide will hopefully help with that: https://www.ti.com/lit/ug/sllu335a/sllu335a.pdf?ts=1686769747322&ref_url=https%253A%252F%252Fwww.google.com%252F

    (You could just use your Ki value to calculate your Kp for the specific tuning purpose of improving speed regulation in the below screenshot)

    For just spinning the motor without using MPET, setting SPD_LOOP_KP to 0x001 may also work:

    Best,

    Robert

  • 0 in reply to Robert Wedan
    Prodigy 210 points

    Hi Robert,

    OK, I think I am out of the woods.  I finally got my board running the blower.  The last piece of the puzzle was the wrong value cap got stuffed for the charge pump.  We didn't have 47nF on hand, so I thought I would try 100nF, but 100pF accidentally got stuffed.  The results were surprising.  This caused the buck regulator not to work, I guess since the charge pump powers the gate driver for the high side MOSFET in the buck regulator.

    Thanks to you and Vishnu for your help.

    Dave Gustavson