MIP vs. ULP

Comparison of two energy-saving LCD technologies

by Ralf Helfenstein | reading time: 5 minutes

Introduction

Especially for battery-powered devices or applications with a “weak” power supply over bus systems, there is a need for energy-saving display solutions. Besides E-Paper displays and classic passive LCDs, two lesser-known liquid-crystal-based display types, called ULP and MIP, can also be considered for such use cases. In this report, we focus on these two technologies.

Description ULP Display (Ultra Low Power)

A ULP display is essentially a conventional TFT, but with the following deviations:

Transmissive vs. reflective construction
Conventional TFTs are transmissive and always require a backlight to be readable. ULP displays, on the other hand, are built either transflective or reflective. This makes it possible to read the content without a backlight when ambient light is sufficient.

Refresh rate
A normal TFT has a refresh rate of at least approx. 60 hertz, while a ULP display can be reduced to below 1 hertz.

Operating voltage
In addition, the display controllers are designed to operate with a low voltage of only 1.8 V.

Interface
ULP displays are driven via a standard SPI or parallel MCU interface.

Description MIP Display (Memory In Pixel)

MIP technology and traditional TFT technology differ in several aspects:

Integrated pixel data memory
In a MIP display, each pixel has its own memory, storing its current state. This means that only those pixels that need to change their content must be updated, which significantly reduces power consumption.

No per-pixel memory in classic TFTs
Traditional TFTs do not have integrated memory per pixel. All pixels must be refreshed regularly, which consumes more energy.

Reflective/transflective design
As with ULP displays, MIP displays are built either transflective or reflective.

SPI interface
MIP displays feature an SPI interface through which the display content is modified. Power consumption during updates depends on the number of pixels that need to be changed.

No separate display controller
A MIP display does not have a separate display controller. The logic and frame memory are integrated into the TFT array.

Comparison MIP vs. ULP

Parameter	ULP	MIP
Custom design implementation	Good: Every TFT manufacturer is generally capable of producing a custom ULP.	Poor: Currently, only KYOCERA and SHARP have the rights to offer this technology.
Tooling costs and unit prices	At the «normal» level of a custom TFT development.	High, as only two Japanese manufacturers offer this technology.
Availability of standard products	Poor: Only very few standard displays are freely available.	Good: Both SHARP and KYOCERA offer a wide range of standardized displays.
Contrast	Good	Very good
Color representation	Yes (up to 64 colors)	No
Data transmission and image update speed	Fast	Slow
Power consumption	Advantage with frequent image updates.	Advantage with static image content.

In summary, each of these technologies has its respective strengths and weaknesses.
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