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DRV8350: Hi-Z States of Gate Driver

Shotaro Sakai
Expert 3410 points
Part Number: DRV8350

Hello team,

The output stage, GHx, and GLX of gate drive have pull-down resistors(=150kΩ). But is the logic indeterminate?

Best regards,

Shotaro

  • 0
    TI__Mastermind 26046 points

    Hi Shotaro-san,

    During the logic indeterminate state (input voltage is between VIH and VIL), the device will be either  a logic high or logic low, but is not guaranteed to know which state the device the gate drivers output will be in. 

    If logic high, then IDRIVE will be applied so GHx = SHx + VCP or GLx = SLx + VGLS; and therefore VGS > Vth to turn on the MOSFET gate. If logic low, then IDRIVE will be applied so GHx/GLx is pulled down internally to SHx/SLx; and therefore VGS < Vth to turn off the MOFET gate. After IDRIVE is applied (for TDRIVE time), there is an IHOLD current used to hold in place the MOSFET gate. 

    When the gate drivers shut off (due to a fault, or ENABLE going low), the gate drivers get pulled down to the sources using a passive and semi-active pulldown. The 150kohm resistor is a passive pulldown to slowly pulldown the MOSFETs gates for about 400ns, then an internal active pulldown pulls the gate down to the source voltage. 

    Thanks,
    Aaron