Led driver help

Discussion in 'The Projects Forum' started by tc61, Jul 9, 2011.

  1. tc61

    Thread Starter New Member

    Feb 11, 2009
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    0
    Hello,

    I was wondering if someone could take a look at this LED Driver I am working with and tell me how the Control Inputs are used. They look like simple on off inputs but I don't know if they are routed to ground to be on, or you need a voltage input to trigger the on off.

    I attached the cut sheet with the diagram on it. The CTL 1, 2, 3 are what I am looking at.

    Thanks in advance

    Tim

    http://www.diodes.com/datasheets/AL3159.pdf
     
  2. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,677
    2,729
    The data sheet is quite clear. An CTL input voltage of less than 0.4V is considered a '0', and greater than 1.4V is considered a '1'. The combination of 1's and 0's determine which LEDs are on.
     
  3. tc61

    Thread Starter New Member

    Feb 11, 2009
    9
    0
    thanks for making it "Quite Clear".
     
  4. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
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    There is a truth table on page 6. It is positive true logic.
     
  5. tc61

    Thread Starter New Member

    Feb 11, 2009
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    0
    What threw me off was the

    Absolute Maximum Ratings table...
    VCTL1,2,3 CTL1, CTL2, CTL3 to GND Voltage -0.3 to VIN +0.3 V

    thanks for the help guys..

    have a good weekend
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    This simply means that if your inputs go lower than GND or higher than VIN that the IC will be destroyed.

    What's not obvious is that if you have a long signal path from your controlling unit to the IC, and the signals have low transition times, the inductance of the signal path and the capacitance of the IC's input pins comprises a series LC circuit that will "ring" at high frequencies. Adding resistance in the signal path at the IC's input will help to eliminate the ringing, as in the attached simulation.
     
    Last edited: Jul 10, 2011
    #12 and KJ6EAD like this.
  7. #12

    Expert

    Nov 30, 2010
    16,278
    6,791
    Lord_Baube could have used this last week, but he never posted a drawing, so we couldn't be of much help. Keep it handy. He might come back.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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