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LM5112 gate driver pull up resistance

Vivek Alaparthi
Prodigy 20 points
Other Parts Discussed in Thread: LM5112

Hello,

I am using LM5112 gate driver in my circuit. I am not using IN pin. So, it must be pull up to Vcc. There are no specifications given in the datasheet for calculating pull up resistance. Can anyone suggest me how to calculate pull up resistance for the LM5112 gate driver.

Best  regards,

Vivek Alaparthi.

  • 0
    TI__Prodigy 320 points

    Hi Vivek,

    Looking at the LM5112 datasheet, there is a sink and source current specified when the IN pin voltage  equals VCC and 0V respectively.  The current is less than 1uA so very little current is needed to pull the pin high or low. You must make sure that the pull-up resistance can overcome the 1uA sink/source current that the in pin may have. This means that even a 1MEG would work to pull the pin above the rated high threshold voltage.

    However, a 1MEG may not give the desired AC characteristics that you need for switching.  The input capacitance and external pull-up resistance will affect the rise time of the IN pin itself.  Reducing the pull-up resistance to 10K-100k will ensure a fast rise time for the IN pin.

    Best Regards,

    Dan

  • 0
    TI__Guru* 78070 points

    Hello Vivek,

    Thank you for using the LM5112.  The IN pin can be tied directly to VCC without additional pull up resistor.  Of course you can add 1 Kohm or so as the pullup resistor.

    Best Regards,

    Youhao Xi, Applications Engineering, TI SVA-PPD