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LM3421: Schematic review

daniel
Genius 5095 points
Part Number: LM3421

Hi Team,

Please kindly help to review my schematic.

Any suggestion would be helpful.

Many Thanks

  • 0
    TI__Mastermind 25500 points

    Hello Daniel,

    It's hard to be sure of all of it without the operating specs (input voltage, LED stack voltage and current), but here are the comments I have so far:

    1. I'm not sure D801 is necessary unless it is for a reason I'm not aware of. D802 and L801 already provide a path from Vin to Vout as in any boost converter.

    2. I am assuming the LED current is not very low given the FET used and that L is a 3A inductor (I'm not sure if that rating is sufficient without knowing the specs). In either case, unless it is much lower than I expect, R808 and R809 look to be very undersized if I'm reading this correctly. They look to be 0603 size resistors which are very low power. Those two resistors will likely need to dissipate significant power.

    3. The input and output capacitor values are extremely small. They should both probably be in the 1's to 10's of uF range total at a minimum and depending on the operating specs maybe more.

    4. I would put R828 at 10 ohms and C801 at 0.1uF.

    The rest looks ok from what I can tell. Just follow the datasheet equations to make sure your inductor saturation current rating is sufficient for your application.

    Regards,

    Clint