It’s everything that got upgraded in the tablet, but mostly the LEDs
Raymond Soneira, president of DisplayMate Technologies, suggests the temperature at which the iPad 3 operates is nothing short of a miracle, considering all the factors that come into play when the tablet is running at full brightness."The LED power at maximum brightness is 2.5 times that of the iPad 2," Soneira said in a telephone interview with the people at CNet.
Soneira explained that “[Apple] had to jack up the number of LEDs so the peak brightness is the same as on the iPad 2. That absolutely makes it warmer," he said.
Soneira carried out his own tests and found that the new iPad didn’t get uncomfortably warm when held in hand.
However, he did wish to highlight four key factors that contribute to the tablet’s warmer operating temperature. From the report:
1. Twice the LEDs: That means more heat coming from more LEDs. This is especially a problem at full brightness.
2. 2.5X the power needed: The brightness efficiency is lower because the new iPad has more pixels (which means more transistors) compared to the iPad 2. More pixels and transistors take up more space, meaning less opportunity for light to pass. "So they basically have to blast light through the LCD to make it come out." Soneira adds: "I measured the LED power at maximum brightness--it's two and a half times greater than on the iPad 2."
3. Battery generates more juice: The battery has to push out more power. This makes the battery warmer.
4. Traditional LCD technology: Sharp's power-efficient IGZO technology was not ready for the new iPad. That forced Apple to use traditional--and less power efficient--amorphous silicon tech.
Soneira concluded that, “not only do the LEDs need two and a half times more power but the battery is going to run warmer.”
Apple’s new iPad boasts a 70 percent larger battery, “so what happens is that if you run your new iPad at full brightness, the battery run time is less because you only put in 70 percent more battery but you're using 150 percent more power," he said.