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UCC28951-Q1: UCC28951-Q1

Ahmed Eldistawy
Prodigy 10 points
Part Number: UCC28951-Q1
Other Parts Discussed in Thread: UCC28951, UCC28950

I am testing a board (3.6KW Phase shifted full bridge DC-DC converter) which is using UCC28951QPWRQ1 controller. I am facing a problem which is that the IC  is drawing about 250mA of current at VDD and the voltage at VDD is 9V instead of the 12V that I have on the board.I wanted to know what could make the IC draw all this current and why the voltage at VDD becomes 9V instead of 12V.

  • 0
    TI__Guru* 85926 points

    Hello,

    The UCC28951 should not be drawing that much current.  The device does not drive FETs directly and the VREF short circuit current is -53 mA maximum.  The IDD startup current is less than 270 uA.

    The outputs are not drive FETs directly.  So they should not be loading down VDD.

    I would ohm out all the device pins to make sure nothing is shorted to ground.  If everything is O.K. maybe the device got damaged and you could try another device to see if that fixes the issue.

    It might be worth while to get a hold of the UCC28950 EVM to evaluate the design and the designs performance.  The UCC28950 is parametrically the same as the UCC28951.  The only difference is the UCC28951 can be designed for slightly more duty cycle.

    https://www.ti.com/lit/ug/sluub02a/sluub02a.pdf

    Regards,

  • 0
    TI__Prodigy 10 points

    I tried replacing the IC, yet the problem still persists.

    Also the 250 mA are being drawn by the IC and it is getting hot. 

    Do you have any idea why that could be happening?

  • 0 in reply to Ahmed Eldistawy
    TI__Guru* 85926 points

    Hello,

    Did you ohm out the pins to see if anything was shorted to ground or not connected the way it should be?

    Do you have a schematic that you could share for review?

    Check the reference or outputs to see if they are shorted.  The device should not be drawing 250 mA.

    While troubleshooting use a DC bias supply and limit the current to 100 mA so the IC does not get damaged.  That much current could damage the IC.

    Regards,