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Original question:

LP5810: Practicality of driving multiple LED's on single channel

LP5810: Parallel/ganging multiple channels possible?

Mike Neuman
Prodigy 150 points
Part Number: LP5810

Tool/software:

I have a couple LEDs that need to draw up to 100mA. Is it possible to wire the cathode to two channels, and use them in parallel to control up to 100mA draw?

Thanks!

  • 0
    TI__Mastermind 34875 points

    Hi,

    Our expert will reply you early this week....

  • +1
    TI__Mastermind 34875 points

    Hi 

    It's OK to parallel the OUTx pin to sink higher LED current. 

  • 0 in reply to Andy Chen
    Prodigy 150 points

    Thank you, Andy!

    A follow-on question: In another use, I have several common anode 3-color LEDs which I would like to run in parallel (i.e. have two or more 3-color LEDs turn on at the same time)--these are tiny 2-5mA LEDs, so I'd like to connect their respective cathodes to OUTx pins. 

    These LEDs have a pretty large range of Vf for each color, and I want to avoid the problem where one LED draws all the current while leaving the others off. Do you have a recommendation (or app note) for connecting multiple LEDs in parallel to the same OUTx?

  • +1 in reply to Mike Neuman
    TI__Mastermind 34875 points

    Hi Mike,

    do you mean parallel 2 or more LEDs with different VF and connect to one OUT pin?  we have below suggestion:

    1. as the LED current is quite small, you can use as higher as possible VLED to drive the LED bank

    2.  use small current diode (VF=0.7) or Schottky diode (VF=0.3) in series with low VF LED to increase the total VF

    3. Use balance resistor in series with each LED path.

  • 0 in reply to Andy Chen
    Prodigy 150 points

    Hi Andy,

    I'm planning on paralleling multiples of the same 3-color LED. The Vf spec is within a fairly broad range, for example red is 1.6 to 2.4, green is 2.1 to 3.1, blue is 2.1 to 3.1.  So, all the reds (for example) might have different Vf's, but not intentionally or predictably so. 

    The Schottky is a good idea, if I knew in advance one would have a different Vf. The balance resistor might at least keep the current draw somewhat similar between them. Something like 100-200 ohms to keep them within a narrow voltage differential. Is that what you were thinking of?

  • 0 in reply to Mike Neuman
    TI__Mastermind 34875 points

    Hi Mike,

    You are right.

    You may provide more detail information of LED configuration, so we can check how to balance the LED current