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TPS23756 and TIDU190

Bill Sorel
Prodigy 20 points
Other Parts Discussed in Thread: TPS23756

I've built the circuit from TIDU190 utilizing the TPS23756 chip.  It is exactly the same as described in the datasheet except with the AC adapter input section removed.  The trouble is: when using the 12V DC supply input there is no output on the board.   Troubleshooting further from the TPS23756 IP there is no gate pulse, nothing on VC or VB either,  VAPD = 1.92V so the internal hotswap switch is disabled.  The example was designed to work from 10.8V up so it shouldn't be an undervoltage situation.  I've replaced the TPS IC in case it was just a dud but the new one yielded the same results.  I am running out of things to try.  I the used PoE input and the results were the same as the DC input.

  • 0
    Prodigy 20 points

    I've been scouring the data page for some idea's and under GATE on page 10 it says that "GATE is held low when the converter is disabled".  So based on my measurements I'm not getting the VC bias voltage on startup which leads to no VB and gate that would continue to allow the circuit to work.  Could this be a timing issue?  I've more than met the requirements for the startup Cap on VC.  Please help!