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Original question:

TPS61196: Can we connect two LED strings to one IFB pin?

TPS61196: Multiple driver channels to the same LED string - different number of LED's per string

Lenio Cacula
Genius 16730 points
Part Number: TPS61196

My application has a 13.6V input and I need to drive three LED strings at 150mA each. Two of them have 6 LED's, and one has 8 LED's, with 3.2V Vf max each. If I use individual channels, everything works fine. However, with the intent of better dissipate heat in the device, I wanted to use two channels per string. Here is my configuration:

With this configuration, only the string with the largest number of LED's works, in this case the 8-LED fixture. If for instance I modify the diagram above and use 4 LED's where the 8-LED string was, then the two banks of 6 LED's turn on, and the new 4-LED bank stays off. 

Is this the way the part is supposed to work? Any workarounds?

Thank you!

  • 0
    TI__Mastermind 22745 points

    Hi Lenio,

        Here are some commons from my side:

        1. You need to change the resistor connected to ISET pin when you want to use two channel to drive one string since each channel only need to provide 150mA/2=75mA;

        2. You need to pay attention to the section 7.4.1.3 in datasheet for LED short-cross protection configuration and you'd better check the value;

        3. This configuration is ok for our device to support different LED counts for each channel.

    Regards

    Sean