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LM3410: Analog dimming possible?

user559647
Prodigy 30 points
Part Number: LM3410
Other Parts Discussed in Thread: LM3405A, LM3405

Is it possible to create analog dimming with LM3410, by adding an analog offset to the feedback?

(see attached sketch)

The step-down LM3405A can be handled this way, but there are issues at startup

  • 0
    TI__Mastermind 25500 points

    Hello,

    Yes, that is a valid way to analog dim with this device. I have not tried it but it is a common method used with many devices and most do not have startup issues with it. It is good to know that the LM3405 might in case I run into that issue.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Prodigy 30 points
    I will test the LM3410-design I just made.
    An I2C-controlled lampdriver should be made simple.
    A digital pot, OP with voltage reference, and a creap switchcontroller. Then the work is done;)
    If you Google on I2C controlled lamp driver, you're a child nor a design engineer;)

    About LM3405 and current control by FB-offset...
    No not apply FB-offset before EN/DIN is set high, then you will have no problems.
    Some internal secret in the error-amp or flip-flop, can never be found only looking on a block schematic...
  • 0 in reply to user559647
    TI__Mastermind 25500 points

    I could see that happening. It likely depends on all of the internal timing that you can't see in the block diagram. I'm sure some devices, if you have the current sense node already biased, may detect and overcurrent condition or something of that nature if it reads the current sense voltage while the internal reference is still not at full voltage. It is always best to test and always best to sequence just in case like you did with the LM3405. But many devices will have different timing and work just fine even if pre-biased.

    Regards,

    Clint