Cree XM-L2 not drawing enough current

Hi All,

I have a project where I need super bright LED, I chose the XM-L2 based on its datasheet where it states that at 3.18V it draws 3A for an output power of around 10W.

I order those LEDs and when bench testing them, found out that at 3.18V it draws 300mA, tried increasing the voltage to 5V and got 1.3A, to get to near 3A voltage needs to go up to around 7.5V which is more than double of what is expected.

Does anyone has experience with this LED and can explain why such a difference?




Is anyone able to help on this question? I am not sure on an answer to this one. Thank you.


Hi marcelobm.

Can you give the specific part number you’re working with?


What kind of thermal management was provided? Insufficient heat sinking is probably the most common cause of abrupt failure in such devices.

Many are produced as an array of parallel cells on a given die. If some of those cells should fail open-circuit due to overheating, it’s like closing lanes on a highway; traffic can’t move as quickly on a vehicles-per-hour basis unless everybody speeds up. And if people try to drive 180 mph because 2 of 3 lanes on a highway with a 60mph limit are closed for construction, it’s not going to take long before that last lane ends up closing also…

Thanks for your reply, I don’t think that is the case here, if there was an issue with the component temperature, wouldn’t the current drawn be as expected until it gets to the point you mentioned above?

Assuming that the LED in front of you is actually the part number mentioned (it might not be, mistakes do happen…) the only plausible explanation for the Vf being as far off as described would be damage of some sort. Damage due to static discharge might be another possibility.

It’s not a large or massive device; thermal damage can occur very quickly. Applying 3A/7.5v across the device would put over 20 watts into a device with a footprint less than 0.04 square inches; without some very good heat sinking I’d be surprised that such a device would last long enough to make the measurement.

So I’ll kindly ask again: what kind of thermal management was provided? Can you share a photo of the test apparatus? Thermal issues are so incredibly common with these devices that there’s no point in further discussion until that possibility can be ruled out.

Could also be due to wiring. Do you measure the voltage drop at the LED or at the power supply? 1 ohm resistance in the wires can already explain this.