Samsung Galaxy Note 20 Ultra brings in several big and small refinements over the Galaxy S20 that didn’t get much mention at the launch. One very exciting change is the technology used for the display.
Samsung is using an LTPO AMOLED panel that it brands as HOP (hybrid oxide and polycrystalline silicon) – the same kind that Apple and Samsung have used on their smartwatches for a couple of years, and the kind that will reportedly be used on the next-generation iPhones.
What is an LTPO Display? What are its advantages?
LTPO, which stands for low-temperature polycrystalline oxide, is shaping up to be the next-generation technology for premium phones and wearables. It basically combines LTPS and IGZO for the display backplane. In LTPO panels, the switching circuits use LTPS TFTs and the driving TFTs use IGZO materials. This helps reduce power consumption by 5 to 20 percent.
LTPO technology is applicable to both LCD and AMOLED panels, but it will most likely be developed only for high-end AMOLED display phones.
Another significant advantage of LTPO technology is that it makes devices that can dynamically change refresh rates possible. This is how Apple could implement a workable Always-on mode on Apple Watches that pushes very few frames in static mode and helps conserve battery.
And as Mishaal Rehman from XDA pointed out, that’s probably how Samsung has managed to add a true variable refresh rate on Samsung Galaxy Note 20 Ultra.
LTPO Vs LTPS vs IGZO: What’s the difference?
The base layer of an AMOLED panel is a Thin Film Transistor (TFT) backplane that provides current to OLEDs, thus determining their brightness. In other words, it is this layer that turns individual pixels on and determines how bright they glow.
Amorphous Silicon (a-Si) TFT technology used to be dominant for display backplanes. With a need for high resolution and brighter screens, the industry shifted to LTPS TFT backplanes (for both OLED and LCD), and then the need for higher resolution and high-refresh-rate brought in more complicated IGZO TFT (Oxide TFT) panels.
LTPS (Low-temperature polycrystalline silicon) backplanes have higher electron mobility and thus can turn pixels on/off faster. Or transistor size can be reduced and more transistors can now be added within the same space, thus resulting in more pixels or higher resolution. However, along with faster mobility, LTPS panels also have higher leakage.
IGZO (indium gallium zinc oxide) backplane technology or transistors used in backplanes that are often used for IPS LCD displays. IGZO transistors are transparent and thus IGZO backplane displays require less backlight power and consume less power. Electron Mobility of IGZO is as high as LTPS and these displays are more touch-sensitive (we are guessing use of IGZO in Samsung Galaxy Note20 Ultra’s display plays a major role in reducing S Pen latency to 9ms).
IGZO, however, has some disadvantages. The uniformity of electron mobility is less than LTPS.
So, LTPO display combines the benefits of both LTPS and IGZO resulting in a more responsive screen that consumers lesser power than conventional LTPS screens. As stated above, in LTPO panels, the switching circuits use LTPS TFTs and the driving TFTs use IGZO materials.
What? Don’t current phones already have variable refresh rate displays?
As we discussed a while back, phones don’t have a true variable refresh rate. The biggest power draw in current high refresh rate phones are the display panel and display driver ICs.
Most modern phones keep refreshing at set frequencies or switching between different frequency presets even while displaying static content. DDICs working this way have to work harder and naturally waste more power.
Android phones like ROG Phone 3, OnePlus 8 Pro and Galaxy S20 do have variable or adaptive refresh rate modes implemented on a software level. In such modes, the displays can change refresh rate but only to certain predefined settings – 720@60Hz, 1080@60hz, 1080@90Hz, etc.
The Galaxy Note 20 Ultra, on the other hand, reportedly has true variable refresh rate. The display refresh could be as low as 10Hz while reading articles or vary from 30 to 120Hz while playing games.
The true variable refresh rate will help save power, but the actual impact remains to be seen.
Why Samsung Galaxy Note 20 Ultra doesn’t support 2K resolution at 120Hz?
Samsung hasn’t really cleared the air why. The Exynos 990 chipset is capable enough and the use of LTPO panel with true variable refresh rate further simplifies things.
Last Samsung flagship, the Galaxy S20, has a single channel MIPI interconnect between the chipset and DDIC, and this single lane highway is probably why it can’t manage the bandwidth required for 2k@120Hz (in comparison, the OnePlus 8 Pro that has dual-channel MIPI interconnect).
The same single lane interconnect could also be the reason for the omission on the Galaxy Note 20 Ultra, or maybe Samsung wants to maintain some feature parity between 2020 flagships and is saving 2K@120 for the next year.
Phones with Dynamic Refresh rate LTPO Displays
The list is currently quite short, but we will add more phones as they surface.
- Samsung Galaxy Note20 Ultra
- Samsung Galaxy Z Fold 2
- iPhone 12 Pro and iPhone 12 (upcoming)