• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 62 subscribers
  • Views 705 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM3466 Demo Board.

George Rasko
Prodigy 30 points
Other Parts Discussed in Thread: LM3466

The LM3499 Demo board is five channels, each set to 0.35 amps.

If I connect three LED strings (leave two channels open), will the three strings current regulate to 0.35 amps each (1.05 amps total)?

Or, will the board try to regulate to the total of 5 x 0.35A = 1.75 amps? [1.75/3 = 0.58 amps per string]

If the answer is 1.75 amps, how do I turn-off the two unused channels?

  • 0
    Prodigy 30 points
    oops
    Should be "The LM3466 Demo board is five channels ...."
  • 0 in reply to George Rasko
    Guru 23000 points
    The LM3466 is meant to spread the Input current to all remainder LED strings.
    If your Constant Current Supply is able to deliver 1.75A this will be equal spread over all available LED strings.
    If you have 3 active LED strings each will get 1/3 of the current = 0.583A
    If you have 5 active LED strings each will get 1/5 of the current = 0.350A
  • 0 in reply to Leo Bosch
    Prodigy 30 points

    Thanks.

    So, please confirm ....

    1. If I want to use the demo board to drive three strings at 350mA, I need to 

    lift the current sharing pins on the two unused chips.

    2. With two chips disabled, and the three channels at 350mA, if I have three

    30 volt LED strings, and a 35 volt/2 amp power supply (i.e. no current limiting in the feed), the three active

    chips will each have 5 volts across the internal FET, each string will

    have 350mA current in it, and each of the three chips will each be dissipating 5 x 0.35 = 1.75 watts

  • 0 in reply to George Rasko
    Guru 23000 points

    George Rasko said:

    1. If I want to use the demo board to drive three strings at 350mA, I need to 

    lift the current sharing pins on the two unused chips.

    No, you have to do nothing.

    George Rasko said:

    2. With two chips disabled, and the three channels at 350mA, if I have three

    30 volt LED strings, and a 35 volt/2 amp power supply (i.e. no current limiting in the feed), the three active

    chips will each have 5 volts across the internal FET, each string will

    have 350mA current in it, and each of the three chips will each be dissipating 5 x 0.35 = 1.75 watts

    This setup is DANGER!

    You will destroy your LED’s and/or blow up your Power Supply.

    You absolutely must use a ‘Current Regulated Power Supply’.

    In your case the power supply current limit must be 1,050mA.