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Smoke of TPS54327

takahiko yokota
Mastermind 7135 points
Other Parts Discussed in Thread: TPS54527, TPS54327

Hi

My customer uses TPS54527.
When they let it short-circuit between VIN and VBST terminal, 
this devise emitted smoke.
As long as I read the datasheets of TPS54327 and TPS54527,
these devise are same functions.
So I concern emitting smoke about TPS54327 like TPS54527.
Does TPS54327 have fear smoking?
I will suggest to insert fuse into VIN terminal.
Is this correct as countermeasure?
Best regards,
Yokota
  • 0
    TI__Expert 4875 points
    Hi Yokota,

    VBST pin is used to charge the bootstrap capacitor which supply power for the gate drive circuit of the high side NFET. The absolute maximum rating for the voltage difference on VBST pin and SW pin is 6.5V. SW is the switch node pin which can swing between Vin and ground level. In your case, if you short Vin pin and VBST pin, the voltage difference between VBST pin and SW pin will be higher than 6.5V, when SW is pull down to ground. This will cause failure and thermal issue to the gate drive circuit of the high side NFET. This should be the reason for the smoke problem. My suggestion is to use the internal 5.5V to supply power for the gate drive circuit, which means no connection between VIN pin and VBST pin.

    Best regards,
    Anthony
  • 0 in reply to Anthony Lang
    Mastermind 7135 points
    Hi Anthony-san

    Thank you for the answer and sorry to bother you again.
    If VIN-VBST terminal interval was short circuit, does VREG5 terminal brake?

    Best regards,
    Yokota
  • 0 in reply to takahiko yokota
    TI__Guru**** 191445 points
    I probably have open/short pin test results. Let me check for it.
  • 0 in reply to takahiko yokota
    TI__Expert 4875 points

    Hi Yokota-san,

    The design team conducted the pin to pin short test. The test condition is Vin 12V, Vout 1.05V, Vin current limit : 4A ,  Io 2A. If EN=low before VIN-VBST short, during the short test time, TPS54327 is broken. After the short circuit is removed and EN=high, TPS54327 stopped operation and is not functional. The output voltage will go to 2.187V and the output current is 0. If EN=high before VIN-VBST short, during the short test time, TPS54327 is also broken. The input power supply current limit is triggered and TPS54327 is not functional after that and there is an extreme high temperature on the IC. So in one word, TPS54327 cannot withstand VIN-VBST in short. For the test, It does not show whether VREG5 terminal is broken, but since the IC does not work any more, it shows us that short between VIN and VBST is not allowed. 

    Best regards,

    Anthony