LED selection and heat characteristics

Hi - I am looking for some guidance for selection between the following CREE Led’s:

XTEAWT-00-0000-000000KC1 - 156 Flux @ 85 degrees
XTEAWT-00-0000-000000GC1 - 139 Flux @ 85 degrees

Given the KC1 part has higher Flux, when both parts are driven at the same 350mA, would the KC1 part generate more heat, or would they both operate at 85 degrees? If not, how does it achieve the higher flux rating?

I am looking to minimize heat generation, but would like the higher flux rating.


They are both being driven by 350mA and operating at the same temperature when the flux is measured. In order to get the same flux from the second one you would need to increase the current which would in turn increase the temperature. If you’re trying to maximize flux and minimize heat generation then get the highest value you can @85 degrees.

Thanks Shawn!

You’re welcome.

Thanks Shawn – one more follow up question:

In the case of CREE part number XPLBWT-00-0000-000BV50E3, assuming it is the case that it can be driven at 1050mA, to produce the 470 lumens, and will reach a maximum heat of 85 degrees at this amperage?



@david3, it will be your goal to keep these LEDs from going beyond 85°C. Thermal management is a vital component to driving LEDs properly. If you place these on a small, regular FR4 PCB and drive them with any current over 50mA, they will quickly get hot. Many LED applications use aluminum PCBs for this reason- along with heatsinks, if needed. (The cooler they can be kept, the more efficient they are)

Along with thermal, providing a constant current is also crucial; as LEDs have a range of forward voltages (Vf) when produced (like a bell curve) and that needs to be accommodated for. The ‘typical’ Vf is just that- typical. Many will have a higher and many will have a lower Vf than the ‘typical’ Vf rating.

The “Lumens/Watt @ Current - Test” is your best way to determine which LEDs are the most efficient at converting power (Vf x If) into light.

Kind regards,

  • Between the two you mentioned at first, the KC1 is not normally stocked by us.

Great, thanks Brian.