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TPS40055: Abnormal Pulse

Hirotsugu Kobayashi
Mastermind 9540 points
Part Number: TPS40055

Hi, team.

An abnormal pulse is output in TPS40055.
What is the cause?

CH2:HDRV, CH4:LDRV, CH3:VIN

HDRV is very short cycle, short pulse width is output.
Since LDVR is high, a through current flows and eventually the fuse blows.

  • 0
    TI__Mastermind 40040 points
    Hello Hirotsugu,

    It looks to me something is very wrong. Looking at CH2/CH4 which is the HDRV and the LDRV, they are high at the same time which will cause cross conduction. Also very concerned about VIN dropping suggesting the input supply is going into current limit due to cross conduction?

    I would check schematic and make sure the TPS device is connected correctly from a design perspective. Also I would ensure the board is configured as per correct schematic.

    If you are still are having issues, feel free to reopen thread and post schematic and switch node waveforms, for us to review and we can take it from there.

    Hope this helps?
  • 0 in reply to David Baba
    Mastermind 9540 points

    Hi David,

    This problem has occurred in equipment which has been about 5 years old in the market.
    Although Fsw is 500 kHz, HDRV is on at an earlier cycle than the internal signal.
    I think that there is a problem in the IC internal circuit itself.

    Since the circuit diagram is sent by private e-mail, please tell me the e-mail address.

  • 0 in reply to Hirotsugu Kobayashi
    TI__Mastermind 40040 points

    Hello Hirotsugu,

    If the device has been working for a number of years reliably and now it is experiencing an issue, it is likely the device has failed?  I would carefully replace the device with a new device and if the issue goes away, then there is certainly an issue with the IC.  

    If you wish to continue the discussion over email and send me the schematic, please email me at david.baba@ti.com

    I will close this thread as a result of taking discussion off line.

    hope this helps?