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I want to simulate a a white power LED from Cree in LTSpice. I searched for a LTSpice model and Cree provided one.

By simply putting in this model in LTSpice I get this characteristic.

Cree LTSpice

I do not understand what I am doing wrong and why I don't get the characteristic from the datasheet like this

transfer characteristic

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  • \$\begingroup\$ It looks like you are putting a 0 OHM VOLTAGE RAMP in to an LED and simulating TerraAmps in time as it gets hotter. (which is not realistic) try a current ramp or add series Resistor and measure V vs I, and not TA vs Time \$\endgroup\$ Dec 25, 2020 at 21:20
  • \$\begingroup\$ @TonyStewartSunnyskyguyEE75 I tried a series resistance before, but I don't get the current output I want. I tried a transfer characteristic I vs. V and if I try to pick a series resistance, so that the current output ranges between 100mA and 1000mA, the transfer characteristic is more flatter than in the datasheet \$\endgroup\$
    – Maxim
    Dec 25, 2020 at 21:32
  • \$\begingroup\$ @TonyStewartSunnyskyguyEE75 LTspice D does not model self-heating natively (how could it? - there are no thermal parameters in the model) \$\endgroup\$ Dec 25, 2020 at 21:40

2 Answers 2

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You have the labels backwards so the model isn't being loaded. Should be:

enter image description here

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  • \$\begingroup\$ This is embarrassing, thanks \$\endgroup\$
    – Maxim
    Dec 25, 2020 at 21:41
  • \$\begingroup\$ @Maxim Took me a good 5 minutes of fumbling with your circuit to realize it, so don't feel too bad. \$\endgroup\$ Dec 25, 2020 at 21:41
  • \$\begingroup\$ Oh, no way! I don't think I ever would have caught this. 5 minutes is an olympic world record. Took me 5 minutes even with the answer in front of me to see it. \$\endgroup\$
    – Ste Kulov
    Dec 26, 2020 at 17:59
  • \$\begingroup\$ Good catch! Especially since the label placement is arbitrary (you can drag the labels into the opposite positions and it will look the same either way). \$\endgroup\$ Dec 26, 2020 at 18:26
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Offhand I'm not sure what you are doing wrong, but when I use that model I get good results:

enter image description here

Axis adjusted to be similar to datasheet graph:

enter image description here

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