Thin Film Transistor (TFT) displays are a standard component in most contemporary devices. They possess high color accuracy, fast response time, and high resolution, and this has made them popular in most industries. Knowledge of the interfaces used in TFT displays is necessary for maximum performance and compatibility of function. Some of the popular interfaces include RGB, LVDS, and MIPI, and each of these has limitations and advantages.

RGB Interface: Principles and Uses

What is RGB?

The RGB interface operates by transmitting pixel data on three major color channels—red, green, and blue. By adjusting the intensity of each channel, a great range of colors are created. Maximum intensity across all channels, for example, creates white, and zero intensity black. The interface is prevalent in small-display uses, for example, old mobile phones and factory controls.

Signal Transmission

The RGB information is transmitted in parallel, i.e., multiple bits are transmitted simultaneously. In addition to the color data (RGB), synchronization pulses are very significant. HSYNC marks the start of a new line of pixels, and VSYNC starts a new frame. Pixel clock (DOTCLK) controls the refresh rate, and a larger clock frequency delivers more motion quality.

Limitations and Advantages

RGB is simple to drive and offers good color rendition. It’s cheap and simple to implement, and thus it’s used everywhere where these are the most important considerations. Its sole significant disadvantage is its shorter transmission distance—signal integrity is lost with distance due to electromagnetic interference and attenuation. RGB also requires numerous physical connections, making cable and PCB design more complicated.

LVDS Interface: Low-Voltage Differential Signaling

What is LVDS?

LVDS (Low-Voltage Differential Signaling) is an interface technology that transmits data in the form of differential signals with reduced voltage swings. In comparison to RGB, a single signal wire and a reference to ground, LVDS means two wires for data send. The method provides high speed data transmission in low power consumption and is highly applicable in super-large TFT panels (8 inches and above).

Transmission Process

LVDS serializes the parallel data through a serializer and transmits it over differential pairs. The receiver deserializes the data to parallel format for processing by the display controller. This method minimizes power consumption and electromagnetic interference (EMI) with a more stable signal over a longer distance.

Advantages

LVDS suits long distance and high data speed transmission and therefore is more suitable for big TFT displays. LVDS is differential and therefore it has high immunity to electromagnetic interference and hence generates clearer and more stable images. LVDS uses fewer signal lines compared to RGB, and thus it simplifies the connection and makes space-saving design possible, especially for handheld and mobile devices.

MIPI Interface: Mobile Industry Processor Interface

Introduction to MIPI

MIPI Alliance, established in 2003, aims at standardizing mobile industry interfaces for better compatibility of components like cameras, displays, and processors. MIPI interfaces such as the Display Serial Interface (DSI) enable smooth information exchange between display modules and mobile devices with power-efficient, high-resolution display output.

MIPI DSI: High-Speed Data Transmission

MIPI DSI can support video mode and command mode. Command mode is utilized for transmitting configuration commands to the display (resolution, color depth, etc.), and video mode for transmitting high-speed video data. The interface guarantees the transmission of high-speed pixel data, thus the smooth and precise rendering of the image. The high bandwidth of MIPI DSI and low power consumption are vital in mobile devices that require processing much multimedia content quickly.

Advantages

MIPI interfaces, in particular DSI, support high data transfer rates at high speed that are required for high-resolution displays. MIPI also saves power through low-voltage signaling, which extends the battery life of mobile devices. MIPI uses less current than parallel interfaces due to fewer pins, which suits thin and light devices with very little space.

Applications in Mobile Devices

MIPI interfaces have wide applications in mobile devices such as smartphones, tablets, and smartwatches. In smartphones, MIPI DSI is the de facto display and application processor interface and supports high-resolution displays like Quad HD (2560×1440) and above. MIPI DSI interface delivers smooth scrolling, high-frame-rate gaming, and high-definition video playback at low power. Similarly, MIPI interfaces find ample application in tablets too, where they enable efficient data transfer in big, high-quality displays to facilitate reading, movie watching, and productivity applications. For smartwatches, MIPI’s low power and small size are ideally suited to connect processors to small displays.

HDMI Interface: High-Definition Multimedia Interface

Introduction to HDMI

HDMI is a digital interface utilized widely to transfer high-definition audio and video signals. It was developed in 2002 by a consortium of companies like Panasonic and Sony, and HDMI brought together the use of several cables (video and audio) in one cable and made it convenient to connect. HDMI evolved with time in regard to the resolution, bandwidth, and number of features it supported.

Signal Delivery and Characteristics

HDMI uses Transition Minimized Differential Signaling (TMDS) to transmit data with minimal interruption. HDMI carries several video resolutions from 1080p to 8K and enhanced audio formats like uncompressed PCM and Dolby Digital. HDMI also uses HDCP (High-Bandwidth Digital Content Protection) which is used to block unauthorized content transmission.

HDMI on TFT Displays

HDMI is common in TFT displays of TVs, monitors, and projectors. In monitor computers, HDMI offers high-definition gaming, video streaming, and professional applications with clear images. In TV sets, HDMI is the primary interface for external sources such as Blu-ray players and game consoles and accommodates high-definition or even 4K and 8K resolution material. HDMI is used in projectors, which optimize multimedia presentations, either in corporate, academic, or home entertainment.

Comparison of Other Interfaces

HDMI has better transmission quality and range than RGB with audio and video support over greater ranges, as opposed to RGB that can only provide support for small screens. HDMI is also more flexible than LVDS with audio and video support in consumer electronics. Nevertheless, for handhelds, MIPI takes the place of HDMI as it’s smaller in size and consumes less power.

Other Widely Used TFT Display Interfaces (Overview in Brief)

VGA (Video Graphics Array)

The analog video interface VGA, created in 1987, has been used for computer-to-monitor connections extensively. It supports low resolutions, typically a maximum of 1920×1080, and lacks support for the transport of audio. VGA can still be found in legacy systems but is increasingly being replaced by digital interfaces since it has not supported quality signals and resolutions of modern applications.

DisplayPort

DisplayPort, created by VESA, is a digital interface that can handle high refresh rates and high-resolution monitors and is suitable for professional graphics and gaming. It is capable of supporting multi-monitor setups and high-definition audio. DisplayPort is able to provide video resolutions of up to 8K and beyond, supporting demanding applications in media production and gaming.

Kadi Display TFT Displays

Product Range Overview

Kadi Display offers a range of TFT displays to be used in applications ranging from mobile phones to industrial control. The screens range from 4.3-inch screens to larger screens like 10.1-inch screens, all with up to 1200×1920 resolutions. They employ interfaces like MIPI and HDMI to provide high-quality visual outputs to be utilized in medical devices, industrial systems, and digital signage.

Quality and Customization

With over 20 years of history, Kadi Display maintains strict quality control, as attested by certificates like ISO9001 and ISO14001. Customization through the company is available for interface requirements, size, resolution, and environment in a bid to cater to the individual requirements of the clients. Kadi Display’s flexibility to customize has been thoroughly tested with the success of over 100 customized projects in 2023.

Choosing the Appropriate TFT Display Interface

Considerations Based on Application Requirements

For mobile phones, MIPI is the best interface with high-speed data transfer and maximum power consumption. For computer display, HDMI and DisplayPort are widely accepted with HDMI for general use and DisplayPort where higher bandwidth with games and commercial graphics is utilized. Industrial automation systems will typically recommend LVDS as the interface where high-speed transfer over a long distance is needed.

Balancing Cost, Performance, and Functionality

Choosing the right interface is a trade-off involving cost, performance, and functionality. RGB is low performance but low cost, whereas LVDS is an optimal choice for the industrial market. MIPI, while more expensive, is best suited for mobile applications with high-definition display and low power consumption. HDMI and DisplayPort, while more expensive, are best suited for consumer electronics applications with high-definition and high-bandwidth usage.

Conclusion

Generally speaking, selecting the right TFT display interface is most important when it comes to delivering the highest performance. MIPI is more suitable for mobile, LVDS for industrial, and HDMI for consumer. Kadi Display offers a broad selection of displays with various interfaces, allowing customers to select the perfect solution for their product. Contact Kadi Display today to learn more or discuss your project.