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TPS40054 problem

Krisztian Kocsis
Prodigy 70 points

Other Parts Discussed in Thread: TPS40054

Hello!

I'v designed a PSU with TPS40054 (named "MPS Converter") in SwitcherPro Online.

It works well with loads bellow 200-250mA, but with greater loads, the circuit is restarting periodically (outoput drops to 0V, the rises to the nominal output).

I'm using the same components as in the design sheet?

Do somebody have any idea how can I deal with it?

It have to work within the following range: current load 50mA..6A.

BR,

Krisztian

 

  • 0
    TI__Guru 56985 points

    Krisztian,

    This is Peter James Miller.  I am the lead applications engineer supporting the TPS40054 controller.  This sounds like an issue with the current limit being improperly set.

     

    The TPS40054 controller uses the Rdson of the high-side FET to sense the current during the on-time.  Current is sensed by the voltage at the SW pin and this is compared to the ILIM pin, which is dropped from the input voltage via a fixed current through the ILIM resistor.

    If Rilim is not properly selected or the traces from RILIM to the drain of the high-side FET are poorly laid-out, current limit accuracy can be affected.

    Alternately, if an inductor with a lower saturation current (Isat) is selected, current limit can be tripped early.

     

    If you can provide me with a copy of your schematic or a Switcher Pro screen shot, I may be able to help.

      If you use a switcher pro screen shot, please also include the part number and manufacturer for the inductor and output capacitor, since these critical values do not appear on the schematic screen shot.

  • 0 in reply to Peter James Miller
    Prodigy 70 points

    Thanks for the reply!

    I'v found the source of the problem. Changing the value of Rkff solved the problem!