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LTC3855 Enable control issue


I am using LTC3855IUJ#PBF as 10V to 6V buck regulator. we are using both the channels for same voltage generation.

Observed that when I applied 10V to VIN pin, RUN pin of regulator goes high ~4V even though pulled low from external power sequencer.

  • Hello,

    The RUN pin of the LTC3855 should stay low when the sequencer pulls it low. The RUN pin of the LTC3855 is an input only with a 1uA pullup when the RUN pin is low and a 5.5uA combined pullup when the RUN pin is high. Check the connection between the power sequencer and the LTC3855. Also check the power sequencer itself. In addition, make sure the power sequencer is not biased from INTVCC since INTVCC will only turn on until the RUN pins are high (see page 12 of the D/S, Shutdown and Start-Up section, 1st paragraph).

    Best regards,


  • Hi Mike,

    There is no connection between RUN pin of LT3855 & power sequencer as I isolated by removing series 0ohm resistor.

    also INTVCC is not connected to power sequencer by any way.



  • Hello Rupesh,

    It looks like you have found the problem. Let me know if you need any more help.

    Best regards,


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