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LM3550 driving two alternative LEDs

Michael Gilge
Expert 1690 points
Other Parts Discussed in Thread: LM3550

Hi,

I was wondering whether there is already an application using the LM3550 to drive 2 LEDs alternatively NOT simultaneously. We need to switch between LED1 and LED2 by a logic output (GPIO). The respective selected LEDx will be flashed with up to 5A.

Thanks!

Michael

  • 0
    TI__Intellectual 1940 points
    Michael,
    I have not seen an existing application doing this. It should be feasible if you can mux the feedback nodes going back to the device. If a fixed output voltage charge mode is used, the LED- pin does not need to be muxed. The wrinkle here would be if you need to use torch mode with both LEDs. If that is the case, you would probably need to add a switch on that pin as well.

    Greg
  • 0 in reply to Greg Lubarsky
    Expert 1690 points

    Greg,

    thanks for your answer. We do not need the torch mode, just flash. If I do not mux the LED- pin, both LEDs would be connected in parallel, or did I get it wrong. 

    I have included a schematic with 2 LEDs which are being muxed by switching the pins LED- and FET_CON to the respective LED.

    Michael