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LM76005: paralleling with USB-C

Gabriele Lotto
Prodigy 10 points
Part Number: LM76005

Tool/software:

Dear TI team,

I'm using the LM76005 in a 32–38V input to 5V/5A application, with a USB-C connector in parallel at the output used only for testing and debugging purposes. I have a few questions regarding this setup:

1. The datasheet doesn’t provide information about paralleling the LM76005 with another power source. How does the IC behave when 5V from USB-C is connected in parallel with the regulator’s output?

2. What happens if only USB-C power is present and the LM76005's VIN is left floating?

- Does reverse current flow through the IC (e.g., into the input capacitors)?
- Could this cause any issues for the IC?
- What about the case when VIN < VOUT?

3. Is it acceptable to leave both power sources connected in parallel, or would it be better to use an ideal diode (e.g. LM73100RPWR or others) to prevent potential backfeed or other issues?

Lastly, this is the design, could you review it?

/cfs-file/__key/communityserver-discussions-components-files/196/garpez.pdf

Thanks in advance for your help!

Gabriele Lotto

  • 0
    TI__Genius 14916 points

    Hello Gabriele

    Gabriele Lotto said:
    1. The datasheet doesn’t provide information about paralleling the LM76005 with another power source. How does the IC behave when 5V from USB-C is connected in parallel with the regulator’s output?

    Depending on value of Vout IC might go in current limit or reverse current can flow into the IC

    Gabriele Lotto said:
    2. What happens if only USB-C power is present and the LM76005's VIN is left floating?

    If Vin pin left open, reverse current would flow into the Vin through Vout and it would charge input to Vout

    Gabriele Lotto said:

    3. Is it acceptable to leave both power sources connected in parallel, or would it be better to use an ideal diode (e.g. LM73100RPWR or others) to prevent potential backfeed or other issues?

    it is better to use an Ideal diode, reverse current flow can damage the IC. There is parasitic diode of high side MOSFET, and it would conduct when Vin < Vout. As this diode is not designed to carry large current, reverse current scenarios should be avoided. Additionally, if Vout is significantly higher than USB output,

     I = (Vout - 5)/Rtrace will flow into the USB. If Rtrace is small enough, resulting current can leads to operation in current limit and OCP would trigger.

    Gabriele Lotto said:
    Lastly, this is the design, could you review it?

    Sure, I'll take a look and get back to you

    Regards

    Onkar Bhakare