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DRV8308: DRV8308 questions

Mohan Gurunathan
Intellectual 500 points
Part Number: DRV8308

Hello,

I have a few hardware and software questions related to the DRV8308.

1.  If I am not using the FG feature of the device, what is the proper connection for the FG pins (FGFB, FGINN_TACH, and FGINP)?

2.  If I am using the device in "open loop PWM" mode, does the device implement the "Auto-advance" feature ?  Or is "auto-advance" only applicable for closed-loop speed control mode?

3.  In open loop PWM mode, I need more guidance on choosing the register settings for the following registers:

  • SPDREVS
  • MINSPD
  • SPEEDTH
  • HALLRST
  • AUTOADV
  • DTIME
  • AA_SETPT
  • OCPDEG
  • OCPTH

Sorry I know this is a lot of info.  Please let me know if you can help me select the best values for these registers.

Thanks,

Mohan

  • 0
    TI__Guru 62720 points

    Mohan,

    Thanks for posting on the MD forum!

    1. Per the datasheet, FGFB should be connected to FGINN_TACH, FGINP can be floating.
    2. Open loop mode does not use the AUTOADV, only closed loop uses this.

      1. SPDREVS/MINSPD/SPEEDTH - use these parameters to tune if and when the LOCK bit is set, section 7.3.6 describes this.
      2. HALLRST - This controls when the commutation counter resets, use 1 unless you need higher.
      3. AUTOADV - not used in open loop
      4. DTIME - deadtime adjustment, use default unless value needs to change
      5. AA_SETPT - not used in open loop
      6. OCPDEG - use default unless false OCP events are recorded
      7. OCPTH - Use this setting to adjust the trip point of the FET Vds protection. Current flowing through the output FETs combined with their RDSON will generate a voltage drop which is compared to this trip point.

    Regards,

    -Adam