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LP5860T: Why does LP5860/LP5860T family have 18ch constant current drivers?

Kazuya Nakai59
Guru 20760 points
Part Number: LP5860T
Other Parts Discussed in Thread: LP5860,

Hello guys,

One of my customers is interested in LP5860/60T.

At this moment, they have the following questions.
Could you give me your reply?

Q1.
Why do LP5860/LP5860T family have 18ch constant current drivers?
I think it is for 6 RGB LED driving. But it is better for us to drive 8 RGB LED. So 24ch constant current output type is better for us.
Did TI aim to drive as many LEDs as possible in the smallest possible package?

Q2.
Is 18ch constant current the current main stream? 

Q3.
What is the most success application which uses these ICs?

Your reply would be much appreciated.

Best regards,
Kazuya.

  • 0
    TI__Genius 17225 points

    Hi Kazuya,

    Thanks for reaching out!

    Please refer the comments below:

    1. LP5860(T) family is a matrix topology LED driver. Please refer the simplified schematic below, it has 18ch constant current sink and also has 11 line switch to build the matrix topology. Actually, LP5860(T) can support total 198 LED dots, it means 66 RGB LEDs.

    2. I think TI solution is the main stream since our competitor will always copy our solution.

    3. We have designed in our IC for keyboard backlight and most home appliances application.

    BR, Jared

  • 0 in reply to Jared Zhou
    Guru 20760 points

    Hi Jared,

    Thank you very much for your reply and I'm sorry to be late my response.

    I understood that 18ch driver count would be major and target applications
    are keyboard backlight and home appliances.

    Could I ask you a few questions about LP5860(T) family?
    If I should ask questions at a new thread, could you please let me know?

    Q1.
    How long wire length can be allowed between LP586x and LED anode and cathode?
    I think wire has some inductance and constant current would be unstable
    when large inductance is attached to the constant current driver output.

    Q2.
    I think LP5860 can be used for full color matrix LED display.
    If in case of multiple LP5860 using, Is there any way to synchronize SWx(Source SW)
    on/off timing between each LP5860?

    Thank you again and best regards,
    Kazuya.
            

  • 0 in reply to Kazuya Nakai59
    TI__Genius 17225 points

    Hi Kazuya,

    Please refer the comments below:

    1. For the wire length, it does exist unstable phenomenon in some linear LED driver. But for LP586x family, the matrix LED driver we have not met such phenomenon so far. The main reason is because the if the wire is too long that will cause the voltage loss will be large. So, the current will be not enough before the output unstable. Could you please tell me how long the wire you will use? Maybe we can do some simulation to evaluate it.

    2. Yes, LP586x has an external SYNC pin to synchronize multiple device.

    BR, Jared

  • 0 in reply to Jared Zhou
    Guru 20760 points

    Hi Jared,

    Thank you very much for your supports.

    I'm going to introduce LP586x family to some our customers from now. So I don't have specific wire length information. 
    Is 30~40cm OK. I'd like to have rough wire length for introducing the device.

    Thank you again and best regards,
    Kazuya. 

  • 0 in reply to Kazuya Nakai59
    TI__Genius 17225 points

    Hi Kazuya,

    I can do a test to connect a 30~40cm wire on my EVM board. But it's hard to evaluate a specific value for it since it depends on the parasitic inductance and capacitance on the output. I am not sure if the parasitic inductance of the wire is the same as you and if the parasitic capacitance of the LEDs is the same as you.

    BR, Jared

  • 0 in reply to Jared Zhou
    Guru 20760 points

    Hi Jared,

    Thank you very much for your reply.

    If LP5860 was designed with the assumption that the wire length to LED would be long, it would be OK.
    However, it would be helpful for us if you have a limitation data of wire length.

    Thank you again and best regards,
    Kazuya.