LT8336 in shutdown mode

We are trying to use the EN input of LT8336 to turn off output voltage, but we still see 12.2V out with 12.6V input voltage and EN/UVLO 0V. Is this expected behavior or is there something wrong with our design/board?

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  • +1
    •  Analog Employees 
    on Jan 28, 2021 4:50 PM 2 months ago

    Hello,

    the LT8336 ia synchronous Boost regulator, hence it 'features' a DC path from input to output, even when part is in shutdown and even when the catch diode is replaced by a FET. Reason is the parasitic body diode of the synchronous FET.

    If this behaviour is undesired you would need a Boost with explicit 'output disconnect' feature (LTC3121, but different VIn, IOUT performance).

    2nd option would be the SEPIC topology, which offers a coupling cap and has therefore no DC path from input to output.

Reply
  • +1
    •  Analog Employees 
    on Jan 28, 2021 4:50 PM 2 months ago

    Hello,

    the LT8336 ia synchronous Boost regulator, hence it 'features' a DC path from input to output, even when part is in shutdown and even when the catch diode is replaced by a FET. Reason is the parasitic body diode of the synchronous FET.

    If this behaviour is undesired you would need a Boost with explicit 'output disconnect' feature (LTC3121, but different VIn, IOUT performance).

    2nd option would be the SEPIC topology, which offers a coupling cap and has therefore no DC path from input to output.

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