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DRV8323: GHx, SHx, GLx and IDRIVE

Cherry Zhou
Mastermind 22060 points
Part Number: DRV8323

Hi team,

Here're some questions from the customer may need your help:

1)  Power supply to DRV8323H is 18 V. Is the VCP inside the chip also around 18V? GHx and GLX switch MOS tubes according to the input PWM wave, are their output voltage also 18V, i.e. VGS=18V?

2) What is the purpose of SHX controlling the three phase UVW of the motor and input back to the motor drive chip? Just as a VDS overcurrent monitor with VDRAIN or is there any other purpose? 

3) Gate drive current IDRIVE is also output when opening the MOS tube, and is it applied to the MOS tube together? But the MOS tube is opened with Vgs(th), is it also related to the current?

Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Mastermind 26016 points

    Hi Cherry,

    1) VCP is ideally 10-12V above VM when VM=18V. VCP voltage depends on VCP load current (IVCP), which is affected by MOSFET Qg value, PWM switching frequency, and number of MOSFETs switching, or external load on VCP pin. 

    2) SHx is used for a few things:

    SHx is the motor phase voltage, which slews depending on how fast your turn on/off the MOSFET gate with IDRIVE current. 

    SHx is also the sink current path for the high side gate driver. So when IDRIVEN is applied to GHx, the gate current path sinks from GHx down to SHx using a strong pulldown or weak pulldown depending on the state of the GHx output. 

    SHx is also used as a VDS monitoring pin for both the HS and LS MOSFETs. For the HS MOSFET, VDS monitoring is VDRAIN-SHx and for the LS MOSFET, VDS monitoring is SHx-SPx. 

    Finally, high side VGS monitoring is monitored through GHx-SHx. 

    3) IDRIVE determines how fast the MOSFET gate turns on or off, which affects the MOSFET's VDS slew rate. Higher IDRIVE source current values will cause the MOSFET gate to charge quicker, so that the VGS voltage exceeds the Vth threshold faster and turns on the gate faster. Same can be said for the IDRIVE sink current, the higher the IDRIVE value the faster the VGS value will go below Vth threshold and turn off the MOSFET. These affect the VDS slew rates of the MOSFETs, which determines EMI performance and thermals lost in the MOSFETs. 

    The higher the IDRIVE value, the faster the VDS slew rate; the lower the IDRIVE value, the slower the VDS slew rate. 

    Here is an app note for more info: https://www.ti.com/lit/slva714

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    TI__Mastermind 22060 points

    Hi Aaron,

    Thanks for your support.

    And what's the soldering temperature for this chip? 

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Mastermind 26016 points

    Hi Cherry,

    We do not have the specific soldering temperature for this chip, but please check this part's Moisture Sensitivity Level rating (MSL) on the label for the parts and use this document to determine the reflow profile temperature for the DRV8323H MSL rating: https://www.ti.com/lit/pdf/spraby1

    Thanks,
    Aaron