Simulate Cree XLamp XB-D LED LTspice

Question

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.

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

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 — D.A.S., Commented Dec 25, 2020 at 21:20
@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 — Maxim, Commented Dec 25, 2020 at 21:32
@TonyStewartSunnyskyguyEE75 LTspice D does not model self-heating natively (how could it? - there are no thermal parameters in the model) — Spehro 'speff' Pefhany, Commented Dec 25, 2020 at 21:40

user1850479 · Accepted Answer · 2020-12-25 21:38:31Z

2

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

answered Dec 25, 2020 at 21:38

user1850479

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\$\begingroup\$ This is embarrassing, thanks \$\endgroup\$
– Maxim
Commented 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\$
– user1850479
Commented 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
Commented 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\$
– Spehro 'speff' Pefhany
Commented Dec 26, 2020 at 18:26

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Spehro 'speff' Pefhany · Accepted Answer · 2020-12-26 04:11:21Z

2

Offhand I'm not sure what you are doing wrong, but when I use that model I get good results:

Axis adjusted to be similar to datasheet graph:

answered Dec 25, 2020 at 21:25

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2 Answers 2