A2251 L8100 Diode Drop .009V Resistance 2.6Ohm

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  • abajor
    Senior Member
    • Feb 2024
    • 175
    • United States
    #1

    A2251 L8100 Diode Drop .009V Resistance 2.6Ohm

    Trouble shooting an A2251, it is giving me the behavior that all three USB jacks except the DFU port are reading 5.18V .24A, the DFU port draws no current.

    Tried swapping that CD3217 from a donor, that changed to DFU port same behavior the adjacent USB port is now boot cycling, other side un effected.

    Hindsight probably should have checked the diode drops first.

    I removed L8100 to confirm that the PP1v1_S3 rail was "shorted" It reads about 2.4ohm and .009V on diode drop. The HighSide Low Side FETS before L8100 appear to be fine. Proper diode drop with reverse voltage.

    Odd when I inject 1V into the rail it draws about 0.09A I'm not seeing anything heating up on the ram chips at all.

    Has anybody seen this?
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