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TPS53355: TPS53355

Soumya
Prodigy 655 points
Part Number: TPS53355

Hi ,

Can you please help our customer with below inquiry?

I designed a CPU board based on the Intel Camelback Mountain Customer Reference Board.  We found that one of the Texas Instruments Synchronous Buck SWIFT (TPS53355) got damaged (output shorted to GND).  This issue occurs during power cycle. 

 

We found that the +12V of the output of the inductor (L26) has huge spikes.  We suspects that is the caused of the damage to the device.  This circuit is copied from the Intel design.  Please see below for the schematic.

 

Is there anything that needs to be done to reduce the huge spike on the +12V?

 

    

  • 0
    Prodigy 10 points

    Hello Soumya,

    Thank you for helping me to post the inquiry,

    We found the issue was that the input bypass capacitors are floating.  The voltage spikes reduce dramatically. 

    We designed a CPU board is based on the Intel Customer Reference Board (Camelback Mountain).  The Intel CRB design used an inductor on the input side of the POL (TPS53355).  I don't see the datasheet recommend to place an inductor on the input side of the POL.  I wonder, could this inductor cause the POL unstable?  Please see below for the snapshot of the Intel design. 

    Thank you,

    Hue

  • 0
    TI__Guru 56985 points

    Soumya,

    It would appear you did not including the reference design schematic that shows where L26 is located.

    Is L26 connected to the VIN pins or the SW pins of the TPS53355 device?

  • 0 in reply to Hue Tran1
    TI__Guru 56985 points

    Hue Tran,

    The input inductor between the main 12V supply and the VIN of the TPS53355 is intended contain the switching frequency noise generated by the discontinuous input current of the BUCK regulator from propagating across the 12V supply rail.  Unless the resonance between this input inductor and the ceramic input capacitors bypassing VIN to ground causes the VIN voltage of the TPS53355 to become unstable, it should not pose a stability risk to the TPS53355 based regulator.

    In order to help prevent this, it is generally advisable to use a ferrite bead, a high core loss inductor, or include a high-ESR electrolytic capacitor between the inductor and the VIN of the BUCK Regulator to dampen the resonance and prevent instability.