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DRV8305: EN_GATE of DRV8305

Part Number: DRV8305

Dear, All

Customers are testing using DRV8305.
Each PWM signal is turned off. (Low input to INHx and INLx pins)
When EN_GATE pin is High, GH_A and SH_A become high voltage.
When EN_GATE pin is Low, both GH_A and SH_A are 0V.

We also conducted the test with BOOSTXL-DRV 8305 EVM and got similar results.

The voltage value is 1/10. (Display: 1 V -> 10 V)

Please tell me the reason.

Thanks, Masami M.

  • Hi Masami M.,

    What are the settings of the INLx and INHx signals?

  • Hi, Rick-san,

    We input 0V to all INLx and INHx.

    Hi Masami M.,

  • Hi Masami M.,

    Thank you for the information.

    • What is the value of PVDD when you perform this test?  
    • Is there any load on each of the SHx pins?
    • What is the state of the FAULT pin?

  • Hi, Phil-san,

    Thank you for your support.

    Describe the value we measured.

    >What is the value of PVDD when you perform this test?  

    -> The value of PVDD is about 25V.

    >Is there any load on each of the SHx pins?

    -> All SHx pins have the same waveform as SHA.

    >What is the state of the FAULT pin?

    -> The FAULT pin is High Level.

    Thanks, Masami M.

  • Hi Michino-san,

    Thank you for the information.

    • If you connect a brushless DC Motor to the output of the boosterpack, does the voltage on each SHx pin stay low when EN_GATE is high? 
    • The GHx pins are pulled up to VM, but this is not enough to turn on the high-side MOSFETs.  If you turn on one of the low-side gates (GLx), does the corresponding GHx signal go low?


  • Hi, Phil-san,

    Thank you for your support.

    I can not check for a while because I will be traveling until next Wednesday.
    Please wait.

    >The GHx pins are pulled up to VM,

    It is written that GHx is pulled up to VM.
    Does this VM refer to VCPH in datasheet P16?

    Thanks, Masami M.

  • Hi, Phil-san,

    Thank you for your support.

    >If you connect a brushless DC Motor to the output of the boosterpack, does the voltage on each SHx pin stay low when EN_GATE is high?
    >If you turn on one of the low-side gates (GLx), does the corresponding GHx signal go low?

    We will post the observed waveform.

    For DC Motor connected / not connected, the voltage of SHx was almost the same.
    When INL_A is set to High and GL_A is turned on, GH_A and SH_A output low.

    Thanks, Masami M.

  • Hi, Masami,

    Have you solved this problem? I have the same issue when using DRV8305. When the board is power on reset, DRV8305's GHx outputs are HIGH. It is not correct (they are supposed to be LOW).

    thanks,

    Lankor

  • Hi, Lankor-san,

    This issue received another support and it solved.
    When Gate_EN is ON, leakage current flows from the GATE drive circuit to SHx.
    GHx rises due to voltage rise of SHx.
    The countermeasure is to add a pull-down resistor to SHx and adjust its resistance value.

    Thanks, Masami M.

  • Hi, Masami,

    Thank your very much for your info!  I will try it tomorrow.

    What is the pull-down resistor value you are using?  All SHx pins have a 39k/2.2K resistors for voltage divider of SENSx (connected to MCU ADC) on my board, seems still too big resistor value(total 41.2Kohm) ?

    Rgds,

    Lankor 

  • Hi, Lankor-san,

    The set value of the resistor varies depending on the voltage of SHx.
    Since the leak current value of the device varies widely, it is impossible to set an accurate voltage.
    However, when PVDD is sufficiently high voltage, it is considered that when the pull-down resistance value is 41.2 Kohm, about 8V becomes the center voltage.
    Please set the pull-down resistance value for the desired voltage at this ratio.
    Also, if Gate_EN is turned OFF, SHx will be 0V.

    Thanks, Masami M.