Cree announces 3.45-mm LEDs, hits hot 148 lm/W for cool white

Feb. 8, 2012
The Cree XT-E LED matches the widely-used XP-E LED in footprint and price while offering double the efficacy based on the company's newest silicon-carbide manufacturing platform.

Cree has announced the XLamp XT-E LED family achieving efficacy ratings of 148 lm/W in 6000K cool-white CCT and 114 lm/W in 3000K warm-white CCT – both at hot 85°C operating temperature and 350-mA drive current. The new 3.45x3.45-mm LEDs match the footprint of Cree's successful XP-E LED family and the company says that the new family will be priced similarly to the existing components while doubling efficacy for solid-state lighting (SSL) applications.

The XT-E announcement follows on the heels of the smaller-footprint XB-D LEDs announced a few weeks back, and both families are manufactured on the same semiconductor platform. Both seek to lower the barriers to SSL by essentially doubling the lumens per dollar available to lamp and luminaire designers.

About the XT-E, Cree product marketing manager Paul Scheidt said, "It's an affordable price point for the LED. And you get the highest performance and highest efficacy on the market."

Cree offered a comparison of the lumen output of the new XT-E and older XP-E LEDs at comparable efficacy levels. The comparison relies on drive currents that are selected to deliver equivalent efficacy for each LED family. At 100 lm/W, the XT-E delivers more than 300 lm while the XP-E delivers 100 lm – a greater than 3x advantage. Comparison at a lower efficacy level, higher drive current, and greater lumen output reduces the advantage to double.

Energy Star qualification

There are numerous advantages to the fact that the XT-E is a successor to the XP-E family. For example, the LEDs can be easily designed into existing products. Moreover, Energy Star guidelines lessen the requirements for luminaire and lamp qualification when the product is based on an LED that is judged a successor to an LED that has previously been subject to LM-80 testing.

Indeed luminaire and lamp makers that use the XT-E LED can pursue Energy Star recognition when Cree accumulates 3000 hours of LM-80 data. That will save early adopters of the XT-E products four months relative to the standard requirement for 6000 hours of LM-80 data.

Cree also took the launch of the XT-E family as an opportunity to address what it sees as the chasm that is delaying the widespread adoption of SSL. Ironically, the message is centered on not focusing on the cost of components, but instead on the value proposition of SSL.

Cree's Scheidt said, "Some people think that light at any cost is the path across the chasm," and he was referring to companies focused on the lowest priced LEDs in making the comment. Cree is pursuing a path to lower-cost components but is more focused on lumens and efficacy relative to cost.

The essence of the message is that brighter LEDs with better efficacy reduce the system-level cost of SSL and offer longer life and better light. Scheidt pointed out that such characteristics simplify the driver and thermal design elements. Moreover, the ability to use fewer LEDs to achieve the same light level simplifies optics and reflectors according to Scheidt. Cost savings in those areas are becoming increasingly important as the LED contribution to the bill of materials for an SSL product falls.

The message is apparently resonating with Cree customers. "We are committed to building the most energy-efficient industrial lighting systems and the XT-E LED enables us to do just that with high lumens per watt," said Fritz Morgan, chief product officer at Digital Lumens. "The result is an intelligent LED-based lighting system that is driving widespread adoption of LEDs in industrial facilities, with compelling performance and end-user payback."

XT-E product details

The XT-E family spans a CCT range from 2700K to 10,000K. In the 5000K to 10,000K cool-white products, Cree has added a minimum 70 CRI option that it hasn’t previously offered in that range. Such cool-white LEDs are primarily targeted at outdoor lighting where color rendering is often considered less important. Scheidt said that some European agencies as well as the Design Lights Consortium are increasingly requiring a minimum CRI and that drove the decision to offer a CRI minimum in cool white.

Neutral-white LEDs in the 3500K-5000K CCT range feature a typical 75 CRI and can be specified with a minimum of 70 or 80 CRI. Warm-white LEDs in the 2700K-3500K range feature a typical 80 CRI and can be specified with a minimum 70 or 80 CRI.

All of the XT-E LEDs can be driven at a maximum of 1500 mA. And all, including cool-white LEDs, are hot binned at a 85°C junction temperature and at a 350-mA drive current.

At 25°C operating temperature, efficacy tops out at 162 lm/W. In cool white, the LEDs produce 139 lm at 85°C and 159 lm at 25°C, both at 350-mA drive currents.