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DRV8301 Gate Drive Output Resistance

Derek King1
Intellectual 365 points
Other Parts Discussed in Thread: DRV8301, UCC27211A, TPS54160

I'm considering FETs with a large enough gate capacitance and a high enough switching frequency where the switching losses of  FETs are important  (greater than the Rds_on losses at lower current values).

I've tried to model that expected switching losses of the FET uses a model where the gate driver is assumed to have a certain output resistance.

The DRV8301 provides max source and sink current values for the gate driver, but no any resistance values. According to the datasheet: 

V_GX_NORM : Min 9.5V, Max 11.5V

Maximum source current  (peak Vgs of FET equals to 2 V)  : 1.7 A

Maximum sink current (peak Vgs of FET equals to 8 V) :  2.3 A

I've tried approximating the source and sink resistance values using the formulas:

   Rdriver_source = (V_GX_NORM-2V) / 1.7Amp = (10.5V-2V)/`1.7Amp = 5.0Ohm

   Rdriver_sink = 8V/2.3Amp = 3.48 Ohm


Are these reasonable approximations for gate driver's output resistances or should I use something else?

  • 0
    TI__Mastermind 21320 points

    Hi Derek,

    Let me check on this and I will get back to you.

  • 0 in reply to Nicholas Oborny
    TI__Mastermind 21320 points

    Hi Derek,

    The current limitation is not set by a resistor. The current limit is set by the saturdation current of the transistor. Specifying a resistance value for your model may be difficult. It looks like the values you have assumed are reasonable. Let me know what kind of results you get.

  • 0 in reply to Nicholas Oborny
    Intellectual 365 points

    Sounds like the gate driver output is a bipolar device, which brings up another question.   What is the maximum output low drive voltage of the gate driver?   Is it limited to 0.2V by the the bipolar Vce?

    Other TI gate drivers (such as the UCC27211A) give a bunch of specs.  With the UCC27211A, the LO gate driver low-level output voltage is 0.1V typical, 0.05V min and 0.19V max.    Why doesn't DRV8301 have similar specs?   

    The DRV8301 buck converter seems to be based on the TPS54160, is their a stand-alone part that the DRV8301 gate drive output is based on?

    http://www.ti.com/lit/ds/symlink/ucc27211a.pdf

  • 0 in reply to Derek King1
    TI__Mastermind 21320 points

    H Derek,

    Response from the designer..

    "We are using MOSFET instead of bipolar for the pulldown. If they drive a pure capacitive load (for example external FET), the voltage should be very close to zero since there is no current flowing through it. However, during output slew, there could be ~0.6V voltage for the output low due to cgd charge/discharge."

    The DRV8301 is a multichip module. The TPS54160 is the buck converter but the gate driver is a ground up design. There is no equivalent part for just the gate driver.

  • 0 in reply to Nicholas Oborny
    Intellectual 365 points

    Thanks for the response.