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How to manage LED voltages above 60V in Boost-to-ground topology with TLD5097EP/TLD5098EP/TLD5099EP?

MohammedA_41
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How to manage LED voltages above 60V in Boost-to-ground topology with TLD5097EP/TLD5098EP/TLD5099EP?

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:

  1. 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).
    Figure 1.png
     
  2. 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. 
     

    Figure 2.png

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%).

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‎Nov 25, 2021 05:09 AM
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