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TPS54623: What provides the 2.3 uA current to the SS pin and what controls it, internal to the device?

Part Number: TPS54623

I have an application where the device becomes locked up, not providing any voltage, it appears to have the SS cap stuck below 1.4V with the high-side MOSETs turned off and apparently the low-side as well. What sources/controls the SS pin current?

  • Could you share the schematic and some waveforms which show this condition being triggered? Waveforms that I think would be of interest to start out are VIN, EN and SS/TRK.

    Does this design happen to have the SS/TRK pin pulled up in same way or does it only have the cap to ground?

    Here is some detail on how the SS/TRK pin works that may help. When the TPS54623 is enabled the first step is the device tries to discharge the SS/TRK to near ground to ensure startup from 0V. After the SS/TRK pin is discharged to near ground, the current source turns on and the device is allowed to switch. The SS/TRK pin must discharge to near ground before the current source is enabled and the device starts switching.This is why I am wondering if there might be something else in the design pulling up the SS/TRK pin.

  • Hi Anthony,

    The design is proprietary, we do have an NDA with TI but I cannot share it on the forum, it must be kept private or it could cause trouble.

    Someone else did the initial design and I adapted it, it has been used in previous designs also and never displayed this, but I believe the issue is caused by the context in which it is being used.

    The SS/TRK pin connects solely to a 2700 pF cap which connects to ground, as I recall according to the datasheet that would provide a rise time of ~700 msec. Nothing else attaches to the pin. That is what is confounding.

    Lmk where to send the schematic and I will send it to you and a more detailed description of what I observed.


  • Hi

       You can send the schematic to and I will loop Anthony in.