iPhone 13: what is LTPO screen technology?

The iPhone 13 Pro inaugurates a technology that has never been seen before on Apple smartphones: LTPO. Behind this somewhat barbaric acronym is the essential ingredient behind the all new 120Hz displays.

The 120 Hz screen is one of the great novelties of the iPhone 13 Pro. With this improvement, which allows for better display fluidity, Apple joins the ranks of other Android manufacturers who have already adopted this technology. Not to spoil anything, these screens also allow big gains in autonomy thanks to their variable refresh rate. All this is made possible thanks to the use of a particular component: the LTPO backplane. Don’t run away right away, we’ll explain.

Anatomy of a screen

If the screens of our smartphones seem to be constructed from a single layer, when you look closely, the situation is quite different. Between the glass that you tap and the motherboard of the phone, there are 5 or 6 layers of various technologies. One of the most important is backplane technology (backplane in English).

The exploded view of a screen. In 9, the transistors which conduct the current to the pixels // Source: Wikimedia

To put it simply, the latter will allow the pixels of the screen to light up. To build the backplane of a screen, we use a plate of thin film transistor (or TFT for Thin-film transistor), which will act as a switch for pixels and subpixels. It is an essential component which will determine the definition of the screen and its refresh rate, since each pixel needs electricity to function.

What is LTPO?

It is this layer of the screen that has changed on the iPhone 13. The LTPO backplane is an evolution of two old technologies (LTPS and TFT oxide), which will combine transistors from these two production methods on a TFT plate. The technology is specific to Apple, which inaugurates a technique of in-house screen development.

Transistors that use LTPS technology generally have better energy throughput and can move electrons faster. This characteristic is essential for the 120 Hz refresh, because the pixels will have to change state very quickly. TFT oxide transistors are more energy efficient, particularly at low frequencies. This saves the phone battery when there is little movement on the screen (during reading, in standby, etc.).

By combining the two types of transistors, we obtain a backplane capable of varying the refresh frequency, while remaining energy efficient. LTPO screens did not appear with the iPhone 13. Apple has used them on these connected watches since the Apple Watch Series 4, precisely for its benefits in energy management. The technology is now mature enough to reach iPhones.

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