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LM5050-1: Bi-directional Load Switch

Kenichiro
Mastermind 9165 points
Part Number: LM5050-1
Other Parts Discussed in Thread: LM5050-2, TPS2411, LM5060, , LM5069

Hi,

My customer is now considering to have 60V/approx 20A bi-directional load switch with LM5050.
Since customer likes to have bi-directional mode, so they would use  two pcs of FET with back-to-back.
See below post as similar discussion.

LM5050-2 drive two back to back FET's
e2e.ti.com/.../1037204

With this condition, what kind of solution can you suggest?
Is it still the single solution of TPS2411?

Please let me know, if it's can be suggested with LM5050 circuit.

Thank you for your support in advance.
Regards,
Ken

  • 0
    TI__Genius 10370 points

    Hi Kenichiro,

    The LM5050 cannot be used for bi-directional applications. One of the key features of the LM5050 is that it detects reverse current and shuts down extremely fast, hence not bi-directional. OR-ing Controllers, in general, have this type of feature (reverse current detection and fast shutdown).

    With that being said, if you're interested in a uni-directional device then perhaps one great solution would be a two-chip solution that uses back-to-back FET's (for control), and it would add other features such as overcurrent protection, overvoltage/surge/undervoltage protection, short circuit protection, etc.

    TI has created a design using this type of solution and you can find it here: http://www.ti.com/lit/ug/tidu415/tidu415.pdf 

    Best Regards,

    Aramis P. Alvarez

  • 0 in reply to Aramis P. Alvarez
    Mastermind 9165 points

    Aramis,

    Thank you for sharing your idea. It seems that the bi-directional can not be configured with single LM5050. I see.


    By the way, from the discussion below, I do understand that LM5050 can be used as simple high-side switch (or load switch) with OFF pin.
    Correct?

    LM5060 Question
    e2e.ti.com/.../1526814

    In this case, do we still need to use IN and OUT pins?
    Or these can be shorted together?

    Thanks,
    Ken

  • 0 in reply to Kenichiro
    TI__Genius 10370 points

    Hi Kenichiro,

    Unfortunately, the LM5050-1 cannot be used as an on/off switch. The off switch will pull the gate voltage to VIN, shutting off the FET (because of Vgs = 0V in this case),  but the body diode is in the direction of current flow and would still allow current to pass through. The source/drain of the FET cannot be reversed because of the internal zener diode inside the IC, as well as other things (look below).

    But here's the good news. If you don't care about reverse current protection, then I recommend the LM5060 and use the ENABLE pin to shut off the FET. The body diode is NOT in the direction of the current, so this could be used as a load switch. 

    Best Regards,

    Aramis P. Alvarez

  • 0 in reply to Kenichiro
    TI__Genius 12380 points
    Hey Ken,

    Thank you for taking the time to search, find, and reference my previous post on another E2E thread.

    Looking back I realize that my original answer was incorrect. We do not have a fully verified solution for LM5050 to be used as a load switch. For now, recommended solutions would be LM5060 as Aramis had mentioned, or otherwise LM5069 if additional protection features are desired.

    I have updated my previous post accordingly.

    Thanks,
    Alex
  • 0 in reply to Alex Triano
    Mastermind 9165 points

    Hi Aramis, Alex,

    Thank you for sharing your understanding. It's clear that LM5050 is not good option for this case. I would suggest my customer to check LM5060 as well.
    I have opened new post as below. It's appreciated if you look into the post below.

    LM5060: Bi-directional Load Switch
    e2e.ti.com/.../577512

    Also, I'm happy that my post help you to clarify some posts.
    : )

    Thanks,
    Ken