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LM25141: LM25141 with CSD87355

Stephan Schade
Prodigy 150 points
Part Number: LM25141

Hello community

We have installed a switching regulator LM25141 together with the mosfet array CSD87355, during we bringing it into service we noticed that the array gets very hot even without load.
The controller converts 24V into 5V with a maximum 4.5A output voltage.
Here the circuit:    
 
the yellow marked components (marked with "nb") are not assembled.
The Inductor L5 is Wurth 74439370082   8.2µH 13A.
At first we had reduced the resistances at HO, LO and LOL to 1 OHM which significantly improved the performance loss, but still not satisfactory.

My question now: How can you improve the circuit further to eliminate this problem?
  • 0
    TI__Mastermind 27470 points

    Hi Schade:

    do you mean even in no load conditon, the mosfet is stil very hot? 

    1. whether there is short through of high side and low side fet? When high side mosfet turn on and off, whether it will coupling the low side mosfet on? any improve when you add some snubber?

    2. it is better to show the SW waveform in 2-4 fsw cycles with low side and high side drive.

    3. can you try only reduce the turn on speed of both fet with 10ohm or larger resistor and keep turn off resistor is 0 , see any difference? 

    Thanks

    Daniel Li

  • 0 in reply to Daniel Li14
    Prodigy 150 points

    We suspect that the high input capacity (CSD87355) is the cause.
    We want to try again with the CSD87352 if it is better then.
    We had already replaced the gate resistors with 0-OHM resistors, then it got better, but not satisfactorily.
    At 1 OHM, the effect already worsens significantly.

  • 0 in reply to Stephan Schade
    TI__Mastermind 27470 points

    Hi Schade:

    thank you for your info.  Let me know if you need further help

    Thanks

    Daniel Li