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DRV3201, signals on Test points pin Boost(29), SW (30) .

girish karpur
Prodigy 50 points

Dear TI Team,

We are using DRV3201 for BLDC motor control and prepared a HW board same as the application note SLVU846A–January 2013–Revised July 2013.

  • No error on the ERR pin. 
  • We observe , Highside PWMs are shifted from zero and we cannot understand the reason. LOW side pins shows PWM output.
  • We use the same values of 22microH, 10microF and a fast response schottky diode on SW and pin 29.
  • We have not connected MOSFETS. If we connect MOSFETS, we do not see any PWM waveforms.
  • what is the typical waveforms seen on pin 29, 30 and voltage levels? Please share.

Any help available for the above points?

Best Regards

Girish Karpur

Bangalore

  • 0
    TI__Guru** 114905 points
    Hi Girish,Our experts have been notified and should reply soon.
  • 0
    TI__Expert 3555 points

    Hi Girish,

    I answered the question regarding the shifted PWM on the thread here:

    I will provide a waveform for the SW and BOOST pin by tomorrow. In the mean time there is a good explanation in the datasheet starting on page 39 of how the BOOST converter should behave.

    You say that you do not see the gate drivers switching when you connect the FETs. Could you try to do the following:

    1. Disable CSM (hold the pin low instead of high) and try to run the PWM again
    2. Read all of the status registers and record the values
    3. Provide the ERR pin condition

    Regards,

    Will Toth

  • 0 in reply to William Toth
    Prodigy 50 points
    Dear Will,

    Thank you for your valuable feedback.

    We did some more tests today and following are the results:

    Read all of the status registers and record the values:
    --> we read Status Reg 0 and we read back "0" and Status Reg 1, SPI OK bit was 1 and rest of bits 0. Also no error (ERR pin High, which means no error).
    --> Boost PIN and SW is a high freq (I can share waveform tomo) and BOOST pin going upto 26V in case B_EN pin is HIGH.
    --> on pin 31 (across 330mOhm), we expected a triangle waveform of 0.2/0.3V (is it correct) , but we saw a strange waveform.
    --> we connected MOSFETS , and checked the output waveforms on Highside Gates and Lowside gates. Now we get Highside PWM waveforms but floating at a Value close to VS (12v). As long as PWM is pulsing, it comes to 0V , and when no PWM pulses, it stays at 12v instead of 0V.
    LOw side is a good waveform and stays at 0V. Dead time between Highside and low side is also clearly visible.

    I will try your suggestion on point 1 and report tomorrow.


    I hope I have explained it clearly. If required, I could share the waveform tomorrow to make something clear.

    Thanks

    Girish
  • 0 in reply to girish karpur
    TI__Expert 3555 points

    Girish,

    Thanks for the followup. Any waveforms (including signal labels) you can provide will be helpful.

    For the gate driver, the following signals from one of the gates on one plot will be helpful:

    • GHSx
    • SHSx
    • GLSx

    Regards,

    Will Toth

  • 0 in reply to William Toth
    Prodigy 50 points

    Dear Will,

    I have tried to upload the waveforms. In case if its not visible for any reason, please send me your email address and I will forward it to you.

    Could you please share typical waveforms on pin 29, 30 and 31 for us to verify.

    we use 12v VS .

    There are no errors and ERR bit is High.

    Best Regards

    Girish

    DRV3201_waveforms.docx

  • 0 in reply to girish karpur
    TI__Expert 3555 points

    Girish,

    From the last image it still looks like it is compared to ground, otherwise it would look like Image1 - Image2. Are you taking  a true differential measurement?

    Can you put multiple waveforms on a single scope capture? If possible please also include the gate input (IHSx/ILSx). A smaller timescale will also be helpful. If possible these four signals:

    • GHSx
    • SLSx
    • GLSx
    • IHSx

    I've attached a few screen shots in a power point, please let me know if it helps. The BOOST waveforms might be different depending on the load.

    DRV3201 BOOST and Gate Waveforms.pptx

    Regards,

    Will Toth

  • 0 in reply to William Toth
    Prodigy 50 points
    Dear Will,

    Thank you for the attached ppt. We were able to drive the motor with the DRV3201.
    Currently we have some other issues which we are concentrating.

    We will be checking on these waveforms more thoroughly in a week or 2 weeks. We will use the waveforms in your ppt as reference.


    Thank you
    Best Regards

    Girish Karpur