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TPS54620 Lot Issue

Walid
Prodigy 90 points
Other Parts Discussed in Thread: TPS54620

Hi,

We're having an issue on several boards that have the TPS54620 with marking "TI 27I  AXHZ" on top of the IC.  I have other boards that use TPS54620 with different markings that don't have any issues.  The bare PCBs are all identical, from the same lot, so the only difference is the marking on the TPS.  We've built at least 500 of these boards with the no change to the board and the only ones that have an issue are the ones with the "TI 27I AXHZ" marking.  The issue is that the RT resistor is very noisy and the noise is getting into the speaker, which sounds like it's whistling (high frequency hum).  The frequency of the hum can be changed by touching the node between the RT resistor (R67) and the IC's pin 1.  So, my question is, is there an issue with this lot code parts?  Schematic is attached.

Thanks,

Walid

  • 0
    TI__Guru**** 191445 points

    The RT pin is very sensitive to noise.  Can you show your layout?  The RT resistor must be close to the IC and the GND connection should be close as well.  I never recommend touching sensitive nodes.  Can you post a waveform showing the PH waveform for good and bad parts?  I would suggest sending one or two suspect devices for failure analysis.  You should contact your local FAE for that.