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DRV8302 GVDD, AVDD, PVDD all output zero voltage

Other Parts Discussed in Thread: DRV8302, TPS54160

I am building a brushless motor controller for a motor rated at  60V and 80A using DRV8302 to drive the MOSFETs. We are are having some issues with the PVDD, GVDD and AVDD outputs on the DRV8302. We soldered and tested in the following conditions: Room temperature ~20C, chip soldered with solder paste and a hot air gun maxing out at 200C (we did not follow the soldering curve properly)

What's Working:

  • The buck converter seems to be working fine. It gives us about 5.3V on output which is a little high but gets better under small loads.
  • The PWRGD, FAULT and OCTW are all high, indicating no issues with the buck converter or the motor controller

What's Not Working:

  • GVDD, AVDD pins output 0V even when we run a
  • No gate voltage (GH_A, GL_A, GH_B, etc...) when we apply a 0V-5V PWM at 50% Duty Cycle through with H1 M_PWM set high

Things We Are Not Sure About:

  • CP1/CP2 outputs 0V
  • Our SS_TR is currently floating. Is this okay or does there have to be a cap to GND here?
  • BST_BK is an unstable 11V
  • RT_CLK is a stable 0.475V (is this good or bad?)

Any help would be good. You can find our circuit board design here for reference github.com/.../MotorController

  • Hi Mike,

    Can you provide more background on the application?
    What PWM frequency are you targeting?

    The Phase connections are unusual.
    The current limiting resistors in the gate drive may not allow the gates to turn on quickly.
  • Hey Rick,

    Our intention is to run this 3 phase BLDC www3.towerhobbies.com/.../wti0001p to move a >100kg car. The power is provided by a Hydrogen Fuel Cell. We would be targeting a PWM frequency of 10 000 kHz I believe

    What do you mean by the phase connections are unusual?
    Should we replace the current limiting resistors by something with a lower value (or short it)?
  • Hey Rick,

    Are you about about the resistors R1-R6 in the schematic? I added them to avoid ringing.

    Currently when we apply an input PWM signal (10Khz) to INH_(A/B/C) or INL_(A/B/C) we don't get any output signal on GH_(A/B/C) or GL_(A/B/C) on DRV8302.

    Also the readings on DVDD and AVDD are 0V which according to the datasheet should be 3.3V and 6.0V respectively. We have tried 4 different ICs and are having the same problems.

    Rumman

  • Hi Mike,

    Sorry, I was not clear on my comment. R7, R8, and R9 are reducing the gate voltage of the low side FETs. This is not recommended as it increases the RDSon, lowering the overall efficiency of the system.

    More information:

    • The PWRGD, FAULT and OCTW are all high, indicating no issues with the buck converter or the motor controller
      • PWRGD is a indication the buck is working. FAULT and OCTW are indications that the gate driver has no problems. The buck is independent of the gate driver.  

    • GVDD, AVDD pins output 0V even when we run a
    • No gate voltage (GH_A, GL_A, GH_B, etc...) when we apply a 0V-5V PWM at 50% Duty Cycle through with H1 M_PWM set high
      • Are you setting EN_GATE high? If not, the device is in a low power mode.
      • If connected to a power supply, do you see additional current draw when EN_GATE is set high?
    • CP1/CP2 outputs 0V
      • This should be corrected once you find the cause of GVDD/AVDD pins above.
    • Our SS_TR is currently floating. Is this okay or does there have to be a cap to GND here?
    • It is recommended to connect a cap. Please see second to last paragraph of page 15 for more details.
    • BST_BK is an unstable 11V
      • This is correct
    • RT_CLK is a stable 0.475V (is this good or bad?)
    • this is good.

    FYI -- The most comprehensive information about the buck converter is available through the TPS54160 datasheet.

  • Hello Rick,

    Thanks for the help. We removed R7-R9 and it fixed a few things such as 

    • AVDD - now 6.6 V
    • DVDD - now 3.3 V

    Yes we are setting EN_GATE high and yes we see ~40mA current draw when we set EN_GATE HIGH

    The problems we are currently having include

    • FAULT is low (around 0.8V)
    • Gate driver voltage for all 6 MOSFETS is at 0V

    Things we're not sure about

    • When we test across CP1/CP2 we get 170mV at ~500kHz
    • Is the SS_TR cap absolutely necessary? We didn't attach one because the initial torque required to move the car is very large, therefore we wanted the output rise time to be as short as possible
    • The DRV8302 get's hot when PVDD1/PVDD2 are connected to 20V+

    Updated schematic

  • Hi Mike,

    Now that AVDD and DVDD are operational, please measure GVDD when AVDD = 6.6V and DVDD = 3.3V. It should be ~10.5V. If not, please try to determine why it isn't. Incorrect GVDD operation would explain both the faults and the lack of voltage at the outputs.

    Also, please look at both nFAULT and nOCTW with respect to the fault table for possible faults.

    With regard to SS_TR cap, please post this question to the non-isolated dc/dc forum. They are experts on the TPS54160 buck.
  • Hey Rick,

    I am working with Mike on this project. We measured GVDD and got 0.7V on it. The charge pump seem to be working since we get around 170mA at 500kHz across CP1 and CP2 (unless the voltage across the charge pump too low?) We have no idea what could be causing the problems with GVDD.
    Could the MOSFETs (IRFS7530) be too big for DRV8302 to drive?

    On a side note our driver IC also gets pretty hot when we are testing. Is this normal?
  • Hi Rumman,

    Until GVDD is working properly, the outputs cannot operate. Let's focus on it.

    Please check the layout to make sure there is no problem with the GVDD trace.

    Do you have two 2.2uF caps on the DRV8302 GVDD as shown in the schematic? Please remove one and try again.
  • Hey Rick,

    There is only one capacitor C15 on the GVDD on the schematic and the PCB. The trace between GVDD, C15 and GND is pretty long but I ran a continuity test on it and it was working. Could the problem with GVDD come from something else in the circuit?

  • Hi Rumman,

    Thanks. So if I look at the files in the repository, which ones should I look at?
  • Hey Rick,

    Motor_Driver_v4 is the most updated schematic. Please use that as reference.

  • Hey Rick,

    Please look at the v4 files in the repository. They are the same as the v3 files with the R7-R9's taken out as per your previous advice.

    Cheers,