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LM7481-Q1: LM74810-Q1 Bidirectional switch with DGATE usage only

Diego Barranco
Prodigy 20 points
Part Number: LM7481-Q1
Other Parts Discussed in Thread: LM7480-Q1

Hi,

I was planing to use LM74810-Q1 as a bidirectional switch but noticed HGATE (50uA) has a much lower source current than DGATE (50mA).

Could LM7410-Q1 be configured as the image bellow to drive both MOSFET from the same pin?

I assume the CAP will require to be pre-charged in order to the DGATE to source the 50mA but this won't be an issue since VOUT should be powered prior to DGATE being activated.

  • 0
    TI__Guru 57737 points

    HI Diego,

    The intention of having low drive current for HGATE is because the HFET is supposed to turn ON slowly to limit the Inrush current into the output capacitors. 

    In case you use on DGATE to drive both the back to back FETs, you will loose on the inrush current limiting and over voltage protection functionalities. 

  • 0 in reply to Praveen GD
    Prodigy 20 points

    Hi Praveen,

    Checking the absolute maximum ratings of the LM74810-Q1 the maximum C to A voltage is -5 to  85V which means that if there is voltage in the Vbatt but not on Vout the device could fail.

    I believe this would fix the issue:

    Still no inrush protection or OVP

  • 0 in reply to Diego Barranco
    TI__Guru 57737 points

    Hi Diego,

    You can use the LM7480-Q1 with FETs in Common Source or Common drain configuration as shown in images below.

    Using Common source topology in the right side of the image below should solve your issue.