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LM3405 faintly conduct.

Carl Ko
Intellectual 340 points
Other Parts Discussed in Thread: LM3405

We use LM3405 .

error phenomenon(condition : Vin is the state that is still supplied)

 

When Dimming off, is maintained in a state in which the LED is faintly conduct.

Test Condition

: The same phenomenon can be connected to EN / DIM Port to pull down resistance will occur.

Uniqueness

Same state is displayed even LM3405_EVM B'D TEST. .

  • 0
    TI__Expert 3495 points
    Carl:
    1. Please make sure the EN/DIM pin is grounded when you saw the LED faintly conduct.
    2. Please make sure the output cap is discharged. You can add a resistor in parallel with the output cap to discharge the cap when the
    LM3405 buck is off. If the cap is not fully discharged, there will be LED faintly conduct.
    David Zhang
  • 0 in reply to David Zhang
    Intellectual 340 points


    As above, the LED is dimmed and gave a way to introduce the additional resistor in parallel with the output CAP suggested as a solution to cause conduction.

    The engineer experience, rather than the normal solution is considered. Want me to show a different way.

    Same problem will occur even EVM board that has been provided by TI.