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MCF8316C-Q1: Some questions for MCF8316C-Q1 Start and Stop

Alex Wang
Prodigy 110 points
Part Number: MCF8316C-Q1
Other Parts Discussed in Thread: MCF8329A

Tool/software:

Hi TI,

We have some questions for MCF8316C-Q1's start and stop. Could you kindly help to analyze? Thanks a lot.

1.Due to the reverse rotation of the motor was unacceptable, we used IPD as start-up option, but we could see a little reversion when the motor started up. We also changed to test Align or Double Align, and the reversion was alomost the same as the IPD option. Is it normal?

2.There are several stop options such as Coast (Hi-Z), Low-Side Braking, High-Side Braking. What's the advantages and disadvantages of them?

3.Hall sensors are used to indicate the start and end position in our product, i.e, the motor has to stop exactly at the position which lolcates the corresponding hall sensor.

(1)Could Coast (Hi-Z) be used to directly stop the motor when the hall sensor was triggered? And how is the acoustic performance due to the drop from the target speed to zero?

(2)If I want to use the other options such as Low-Side Braking or High-Side Braking, it would take some time to decrease from the target speed to zero and let the motor move a distance, right? Do you have some suggestion to make the motor stop exactly at the position which lolcates the corresponding hall sensor, when Low-Side Braking or High-Side Braking was used?

4.In the description of stop options in the datasheet's section 7.3.19, it says " When motor stop command is received". What's the stop command? I did not find the specific stop command in the datasheet.

Thanks,

Alex

  • +1
    TI__Genius 13920 points
    Alex Wang said:
    1.Due to the reverse rotation of the motor was unacceptable, we used IPD as start-up option, but we could see a little reversion when the motor started up. We also changed to test Align or Double Align, and the reversion was alomost the same as the IPD option. Is it normal?

    IPD should not lead to reverse rotation. Can you monitor the phase current and check if there are pulses like in the image during start up? If the motor is oscillating before beginning to spin into open loop, lower the IPD current threshold. If the phase current in-between pulses current is not getting to zero, decrease the IPD frequency.

    Alex Wang said:
    2.There are several stop options such as Coast (Hi-Z), Low-Side Braking, High-Side Braking. What's the advantages and disadvantages of them?

    Please refer to our Sensorless BLDC Trap and Field Oriented Control (FOC) Motor Stop Options FAQ for a table of pros and cons for these stop options as well as general guidance on when to use which stop option.

    Alex Wang said:
    (1)Could Coast (Hi-Z) be used to directly stop the motor when the hall sensor was triggered? And how is the acoustic performance due to the drop from the target speed to zero?

    Hi-Z could be used to stop the motor although the motor will take some time to stop. The acoustic performance will mostly depend on the motor's construction but generally deceleration and this break mode should not result in a noticeable increase in noise.

    Alex Wang said:
    (2)If I want to use the other options such as Low-Side Braking or High-Side Braking, it would take some time to decrease from the target speed to zero and let the motor move a distance, right? Do you have some suggestion to make the motor stop exactly at the position which lolcates the corresponding hall sensor, when Low-Side Braking or High-Side Braking was used?

    Correct, the motor can take a bit of time to stop when using High or Low side braking but it will be faster than the Hi-Z method. To stop at an approximate position, align breaking would be the best option which is available on the MCF8329A or using Active spin 

    Alex Wang said:
    4.In the description of stop options in the datasheet's section 7.3.19, it says " When motor stop command is received". What's the stop command? I did not find the specific stop command in the datasheet.

    Stop command refers to a 0 speed command.

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 110 points

    Hi Joshua,

    1.

    Joshua Horlander Cruz said:
    Can you monitor the phase current and check if there are pulses like in the image during start up?

    OK, we would book the lab source and monitor the phase current.

    3(2)

    Joshua Horlander Cruz said:
    To stop at an approximate position, align breaking would be the best option which is available on the MCF8329A or using Active spin 

    Could you kindly explain how to use this align breaking? It would reduce the speed to BRAKE_SPEED_THRSHOLD, then force the motor to stay at ALIGN_ANGLE, right? Would it cause the reverse rotation?

    This align breaking option is not mentioned in the FAQ URL, is it faster than the other options?

    Thanks,

    Alex

  • 0 in reply to Alex Wang
    TI__Genius 13920 points

    Hi Alex,

    I do apologize, recently a bug was discovered with the align brake feature which can lead to the device getting into an irrecoverable state. Due to this bug we are recommending to not use the feature going forward. 

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 110 points

    Hi Joshua,

    OK.. So, to make the motor stop exactly at the position, the only option is Active Spin-Down? But in the table of pros and cons for these stop options, it says "Longger timer to completely stop the motor compared to HS/LS braking", if this Active Spin-Down option takes more time to stop, would it lead to longger distance?

    Thanks,

    Alex

  • 0 in reply to Alex Wang
    TI__Genius 13920 points

    Hi Alex,

    A quick method to stop the motor would be to use Active Braking. This breaking method requires some tuning but can decelerate the motor quickly when tuned appropriately, so this maybe the best option for your application.

    Regards,

    Joshua 

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 110 points

    Hi Joshua,

    OK,. we would try this Active Braking.

    Thanks,

    Alex