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LM5050Q0MK-1/NOPB : tOFF(GAETE) Variation

Hi specialist

We refer the datasheet page4 but tGATE(OFF) is specified as typ value for Tj = 25℃.

Could you provide tGATE(OFF) value including variation in all over the temperature?
If not , please provide how to assume variation.

Best regards.

  • Hi Alpha,

    What is your application requirement? Note that using OFF will shut off the MOSFET, but the body diode will still conduct.

    However to answer your question:

    You can get an estimated time by looking at the min and max numbers of Vgs and Igate-off.

    If we assume tgate(off) = response time of OFF comparato) + time to shut off FET, then the time can be estimated as follows:

    486ns (typ) = tresp + ( t = C * V / I)

    --> 486ns (typ) = tresp + 47nF * 7V / 2.8A = tresp + 118ns

    --> tresp = ~368ns.

    C was chosen as 47nF, because that was the test specification for tgate(off), V would be roughly 7V or 12V typ (depending on input voltage), 7V was chosen to calculate a worst-case tresp. Current for Igate = 2.8A typ.


    So the response time of the OFF comparator is roughly 368ns. If Vgate was actually 14V instead of 7V (max spec over temp), then the 118ns time would double. If the Igate was 1.4A instead of 2.8A (min spec over temp), then this would also double the 118ns time to turn off the gate.

    So in total, the 118ns time can quadrouple over temp, leading to 476ns. The 368ns (typ) response time of the OFF comparator will also vary a bit over temp. Overall, the response time should be within 1-2us.

    Thanks,
    Alex
  • Hi Alex

    Thank you for your response.

    I would like to confirm meaning of "Overall,the response time should be within 1-2us".

    Is it right that in the case of using LM5050Q0MK-1 within specification , t_GATE(OFF) max value including temperature variation is 2us?

    Best regards.
  • Hi Alpha,

     

    That is an estimated value. The response time is not spec'd over temperature.

     

    However, the total time equals the reaction time + time it takes for the pull-down to shut off the GATE of the MOSFETs.

     

    The time it takes for the pull-down to shut off the gate can be determined based on the min and max gate pull-down current (spec'd over temperature). The reaction time is not spec'd over temperature, but if you estimate ~4x slower than typical value, then the total response time would be roughly within 2us over temperature.

     

    Note that having parallel MOSFETs will begin to increase the time it takes for the pull-down to shut off the gate.

     

    Thanks,

    Alex