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DRV8308: DRV8308 Parameters tuning

Gabriel Xu
Intellectual 2145 points
Part Number: DRV8308

Hi Teams

I am helping the customer to tune DRV8308's parameter and encounter several problems need your help:

Vin=24V Using 3 single end hall input  Operating in Clock frequency Mode.

  1. I found the FGOUT(Set to output the U hall signal) signal frequency can't match CLKIN signal's frequency (Can't lock the speed) when the CLKIN lower than 30Hz
  2. Can I enable the bypass filter and disable the bypass compensator at the same time.?( The motor fails to start up when the bypass compensator is enabled in many situations.)
  3. What MOD120 used for? Are this parameter only been used in 180 commutations?
  4. Are the hall sensor compensation (relative with "Advance" register) only active in 180 commutations?
  5. Are close loop speed control can only be used in 180 commutations? Can we achieve as low as 400 RPM with DRV8308?

Thanks in advance

  • 0
    TI__Guru** 114905 points
    Hi Gabriel,

    What is the lowest CLKIN frequency you can match? Is the motor capable of operating at 30Hz?

    Have you tried tuning with the document www.ti.com/.../slvua41e.pdf

    Have you read section 9.3 of the datasheet?
  • 0 in reply to Rick Duncan
    TI__Intellectual 2145 points

    Hi Rick

    Yes, I have read Section 9.3 in datasheet. It said DRV8308 is optimized the speed loop to operate in 50Hz-6.7Khz.

    It seems it can't lock the speed in frequency lower than 50Hz.

    Another question is :

    In DRV8308evm user guide, Section 2.3 it said:

    "If you’re unsure of your motor’s number of Hall U cycles per revolution, you can test it by doing this:
    disconnect the 3 phase wires, enable the DRV8308 (to apply Hall power), probe the Hall U testpoint,
    and use your hand to rotate the motor 360° while counting the number of cycles.     "

    I use this method to figure out my motor's pole. But after this test my EVM seems be damage. When I apply Vm to the board and enable the gate driver the fault signal LED light up all the time. Do you have any idea what is happening?