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Original question:

TPS2662: FLT indication if output current is very small?

TPS2663: FLT indication when no load

Y.Ottey
Mastermind 6145 points
Part Number: TPS2663
Other Parts Discussed in Thread: TPS2640, , TPS1663

Dear TI Team

When operating with an input of 24V and no load, the phenomenon that the FLT pin is asserted occurs as shown in the following post.
Probably the Reverse current protection is working as shown in the following post.
https://e2e.ti.com/support/power-management/f/power-management-forum/865182/tps2662-flt-indication-if-output-current-is-very-small

After starting with no load, the load was reduced by about 240mA, but the FLT terminal was still asserted.
(There is no problem even if the OUT terminal has no load. 24V is output)

I would like you to answer the following questions.
1. Is there a problem such as not being able to use other functions if the TPS2640 is operated with the FLT pin asserted?
(I think it's a problem not to be aware of other protections)

2. Is there a way to prevent the FLT pin from asserting under no load?
(I think that Vout is probably higher than Vin when there is no load, but please let me know if there is any countermeasure.)

Best Regards,
Y.Ottey

  • 0
    TI__Guru** 106521 points

    Hi Ottey,

    Thanks for reaching out!.

    I will go through it and get back by weekend.

    Best Regards, 

    Rakesh

  • 0 in reply to Rakesh
    TI__Guru** 106521 points

    Hi Ottey,

    Sorry, I did not understand your first question. Are you talking about TPS2663 or TPS2640 ? The issue remains same for both devices at light load if the system has larger ripple on the VIN causing a reverse voltage condition Vin < Vout.

    To overcome, one option is to use linear ORing devices like LM74700 or LM73100 at the input followed by TPS1663. The other option is to ignore the FLT signal information if Vout and Vin are good, which has to be managed by a microcontroller or additional logic circuit.

    Best Regards, 

    Rakesh

  • 0 in reply to Rakesh
    Mastermind 6145 points

    Hi Rakesh

    I'm sorry that there is an error in the post.
    It's all about TPS26631.

    The countermeasure you have shown is to ignore the FLT signal, but is it a problem to keep the TPS26631 running while the FLT signal is still being output? (If you can continue to ignore the FLT signal, does that mean you can use TPS26631 without any countermeasures?)

    Regards,
    Y.Ottey

  • +1 in reply to Y.Ottey
    TI__Guru** 106521 points

    Hi Ottey,

    Reverse current is a fault that's why the device asserts FLT output. If it is an issue in your application, please use below options

    • Linear ORing devices like LM74700 or LM73100 at the input followed by TPS1663.
    • Ignore the FLT signal information when Vout and Vin are good, which has to be managed by a microcontroller or additional logic circuit.

    Best Regards, 

    Rakesh