Well, it looks like we jumped the gun a day early with the preliminary announcement of the XP-G2, the successor to the venerable XP-G. Cree has let loose the datasheets for the new LED today, so we can fill in a few gaps in what we know it the little light source.
We had a feeling yesterday that this new LED was based on silicon carbide (SiC) technology, and it’s confirmed today. It’s not surprising really considering the amount of effort Cree has been putting into this new substrate technology. As you may have read on other LEDs like the XB-D, SiC has the potential to reduce LED costs by quite a bit. We aren’t sure just yet if the XP-G2 will share this benefit, as the first round of parts to hit distribution have similar prices to current XP-G stock, but that may change here soon once production kicks into full swing.
In the article we posted yesterday, it showed that the XP-G2 will be able to hit up to 139lm/W in higher color temperatures. Some eagle eyed readers may notice that the XP-G and the XP-G2 are both available in 139lm (@350mA) R5 bins, which until recently, have been fairly hard to get with the XP-G. So why is the XP-G2 any better? Headroom is most likely where the XP-G2 will have an advantage, as well as in actual lumens per watt seeing as the forward voltage are slightly different (explained below). R5 bin XP-G2 LEDs are already in distribution, meaning they are having a lot more success in reliably making chips at this output level. With that kind of success brings the potential to push the output ceiling of the XP-G2 higher.
The initial information on forward voltage was incorrect though from yesterday. We are now seeing lower forward voltages on the XP-G2, with voltage performance at higher currents scaling better. This will allow a hair more head room on drivers.
| XP-G | XP-G2 | |
| Vf @350mA | 2.9v | 2.8v |
| Vf @ 700mA | 3.05v | 2.9v |
| Vf @ 1000mA | 3.15v | 3.0v |
| Vf @ 1500mA | 3.25v | 3.1v |
With these new lower forward voltages, the lumens per watt is now higher with the XP-G2. At 350mA, the XP-G cranks out 136.94lm/W (~119.13lm/W @85C, XP-G’s are tested at 25C), while the XP-G2 manages to get 141.83lm/W (@85C) at the same current, and the same R5 bin. This can add up to some pretty decent gains over the original at higher currents. It’s amaizing what small changes in forward voltage can do.
The emission angle is different, as we reported. It’s now down to 115 degrees versus 125 degrees of the XP-G. It looks like they are using a similar dome to the XT-E, which supposedly has a little better light scavenging ability. This results in a slightly taller dome than the XP-G. It’s less than 1mm difference though. This change in primary optic will change the way that secondary optics perform, so don’t expect distribution patterns to be the same from one to the other.
For those wanting to read through the datasheets and compare for themselves, the links are provided below. Keep in mind though that the temperature ratings for each LED are different (25C for the XP-G, and 85C for the XP-G2), so make sure you take that into account when comparing features.
