Driving 3.1 million pixels a big job

DisplayMate Technologies Corporation president Ray Soneira has delved further into the technology behind the new iPad's Retina Display as well as its relationship to the battery and come up with a simple conclusion: the new iPad, operating normally, should run a bit warmer than the previous model. He calls the thermographic portraits circulating the web "overblown" and says the extra heat is the natural consequence of increased power.

The third-generation iPad uses 2.5 times as much backlight power to illuminate the new display at the same luminance levels as the previous model, Soneira found. The high pixels-per-inch (PPI) ratio of the new display makes the LCD have a lower light efficiency and thus power efficiency. The doubled number of LEDs also give off 2.5 times as much heat, but remarkably the new battery in the iPad manages to (mostly) compensate for the increase.

Soneira, best known for clarifying and codifying the meaning of so-called "Retina" displays, praises the iPhone 4 (and 4S) as being the most power-efficient mobile device Apple makes, due to its exclusive use of Low Temperature Poly Silicon (LTPS), a much more power-efficient display than the Amorphous Silicon used in both the iPad 2 and the latest model. The number of backlight LEDs has risen from 36 to an estimated 72 to 82, contributing heavily to the need for a battery with 70 percent more output than the previous model.

He tested the new iPad by running it at maximum brightness and found that the battery was exhausted in 5.8 hours, 20 percent less time than a similar test with the iPad 2, indicating that the increased resolution can also generate more heat, which contributes to battery drain. Soneira also found that maximum brightness consumed 65 percent of the total power used by the device, stressing the importance of both heat-generation and power-consumption in test results. Tests with the brightness at normal levels (middle brightness) showed the new iPad almost exactly matching the previous model, proving heat generation of the display can play a major role in the device's efficiency.

The combined extra heat of the display, the more powerful processor and graphics chip and the heat generated by the battery itself would not be able to sustain the new iPad for long if the heat-dispersal capabilities of the device were not up to par. Apple has issued a statement saying the new iPad operates within the devices' temperature specifications, but users may want to be way of covering the back of the device with a form-fitting enclosure that doesn't also promote heat dissipation.

Soneira calls for future iPads to employ IGZO displays as soon as possible, saying the display technology pushed by Sharp offers even more efficiency and lower cost than the LTPS technology used in the iPhone. After a production delay, Sharp is expected to start supplying displays for iPads along with Samsung and LG Display, though it is not expected to incorporate IGZO technology at this point.

LED backlight spectrum compared

By Electronista Staff

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digital imaging, display, Apple, iPad