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LED Driver ICs Forum Discussions

j_oehmen
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Moderator 10 replies posted 5 replies posted 10 questions asked
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The LED voltage is limited by the pins FBH and FBL (absolute maximum rating is 61 V). There are two options if higher voltages than 60V are required:


  • Place LED current sensing resistor (RFB) at low side with a 2.5V zener diode to ground. This zener diode avoids false short-to-ground (S2G) failure detections at start-up (S2G detection threshold V~FBL,FBH_S2G~ is max. 2V).
    4786.attach

  • Place LED current sensing resistor (RFB) inside the LED string such that FBH/FBL pins will see voltage < 61V in all cases. This solution saves the extra zener diode and corresponding power losses, but requires additional wires for RFB.
    4787.attach


A small signal diode across the LED string is required in both cases in order to enable S2G detection in case of the anode is getting short-circuited to ground.
Then the maximum LED voltage is defined as the ratio of the minimum input voltage to the maximum duty cycle (91%).

This also works for TLD5097EP and TLD5098EP. See also the LITIX Power page.
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