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LM3429: About PWM dimming for LM3429

Satoshi
Guru 19615 points
Part Number: LM3429
Other Parts Discussed in Thread: TPS92691, LM3421, LM3424

Customer is considering PWM dimming for direct connection to output line.

Please see below image. (Red point： PWM dimming)

Is this circuit no problem?

If no problem, is there any reference design for documentation?

If problem, please let me know about possible problem for this circuit.

Best regards,

Satoshi

  • 0
    TI__Mastermind 25500 points

    Hello Satoshi,

    It should work fine, you just may need some small delays in the turn on/off of the series FET. Alternatively you could consider the LM3421, LM3424, or TPS92691 as they all integrate the series FET drive circuitry. If you would rather stick with the LM3429 you could refer to one of the other 3 device datasheets for the typical delays they incorporate.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Guru 19615 points
    Clinton-san

    Thank you for reply.

    For example, LM3424 have internal FET drive circuit and PWM oscillator on DDRV pin.
    (datasheet page 11)
    But LM3429 have not these circuit (and DDRV pin), simply external FET control ON/OFF only.

    If LM3429 have any point to notice, please let me know.

    Best regards,
    Satoshi
  • 0 in reply to Satoshi
    TI__Mastermind 25500 points

    Hello Satoshi-san,

    It should still work fine with the LM3429. As I mentioned, you may just need to introduce some small amount of delay for the series disconnect FET and it will work.

    Regards,

    Clint