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LM3401: Designing with LM3401

Vijay
Prodigy 170 points
Part Number: LM3401
Other Parts Discussed in Thread: TPS922055

Hello Team,
We are planning to use the LED Driver LM3401 for one of our applications.
The datasheet and the user guide of the LM3401 seem to be straightforward so we can simply design the circuit.
However, can you please explain to us the use of the diode below in the block diagram?


Also, I have seen some devices like AL8861Y from diodes incorporated which use a high side current sensing.
Can anyone share the advantages of using a low-side current sensing?

  • 0
    TI__Genius 16550 points

    Hi Vijay,

    1. For the diode you circled in the picture, my understanding is that this diode may have below possible functions:
      1. for ESD protection
      2. to avoid that any negative voltage Vsg (source-gate voltage for the PMOS) that will slow down the turn-on speed of the PMOS
    2. For the comparison between low-side current sensing and high-side current sensing, below are some points for your reference:
      1. High-side current sensing: normally more expensive, but more versatile
      2. Low-side current sensing: normally cheaper, less versatile
    3. I would recommend you switch to the next generation of LM3401, which is TPS922055. We can talk more if you have interest.

    Best Regards,

    Steven

  • 0 in reply to Steven Li
    Prodigy 170 points

    Hello Steven,
    Thank you for your reply.
    Can you please advise the difference between a hysteretic buck converter and a normal buck converter?

  • 0 in reply to Vijay
    TI__Genius 16550 points

    Hi Vijay,

    I am currently out of office. I will reply to you next Monday when I am back to office. Thanks for your understanding.

    BR,

    Steven

  • +1 in reply to Vijay
    TI__Genius 16550 points

    Hi Vijay,

    Hysteretic control, as well as voltage-mode control and current-mode control are just different control methods for buck converter / controller. There are some pros and cons that hysteretic control can bring to you. You can find lots of materials about this on the Internet :)

    Best Regards,

    Steven