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LM5050-1: Designing with LM5050

Vijay
Prodigy 170 points
Part Number: LM5050-1
Other Parts Discussed in Thread: LM74502-Q1

Hello Team,
We are planning to use the OR controller LM5050 for one of our applications.
The input voltage is 54V from a battery.
From the functional block diagram, it seems like we have a charge pump whose output is connected to the gate of the MOSFET, and the gate voltage can never be higher than 14V to the VIN as there is a Zener diode.
Please correct me if I am wrong
So the MOSFET must be selected with a VGSmax of greater than 14V. Please correct me if I am wrong.


Looking for your reply

  • 0
    TI__Guru 57737 points

    Hi Vijay,

    Yes, your understanding is correct. The maximum voltage that the LM5050-1 will apply across the external FET gate-source is only 14V. You can choose a FET which has a Vgs rating of >15V and avoid use of any additional zener across FET gate-source.  

  • 0 in reply to Praveen GD
    Prodigy 170 points

    Hello Praveen,
    Thank you for your reply.
    If I am using a MOSFET in the following configuration as a power switch instead of the load switch/OR controller LM5050 will there be any problem?



    Also, since the MOSFET doesn't have a slew start/soft start, will it shut down the input voltage source due to overcurrent?
    There is no inrush protection when I am using a discreet MOSFET or when using the LM5050.
    The attached video link says we need an inrush current protection.
    Can you please comment on this?

    Just out of curiosity.

    What will happen if I change the connection of the source of the MOSFET to the drain and that of the Drain to the source of the MOSFET?
    Because, in the usual case, the body diode will be in forward bias condition and we will have an output voltage at the drain of the MOSFET.
    When the MOSFET is connected reverse the body diode will be reverse biased and a voltage will be present at the VOUT only when the IC is enabled.
    I believe this won't be an issue as long as the input voltage is below 14V.
    Can you please comment on this too?

  • 0 in reply to Vijay
    TI__Guru 57737 points

    Hi Vijay,

    Please refer to the e2e FAQ below,

    Can an Ideal Diode Controller used as load switch with external MOSFET?

    For load switch or power path ON/OFF control, you can consider using LM74502-Q1 as shown below,

    For inrush current control, you can use an RC across the FET GATE to GND as shown below,