Interface analysis of LCD driver

TTL interface:

The earliest LCD interface, the TTL interface is an interface that transmits data in parallel. When using this interface, it is not necessary to use a dedicated interface circuit on the driver board side and the LCD panel side of the liquid crystal display, but output by the main control chip of the driver board. The TTL data signal is directly transmitted to the input interface of the LCD panel via the cable. Due to the high signal voltage of the TTL interface, many connections, and long transmission cables, the circuit's anti-interference ability is relatively poor and it is prone to electromagnetic interference (EMI). In practical applications, TTL interface circuits are mostly used to drive small size (below 15in) or low resolution LCD panels. The highest TTL pixel clock is only 28MHz. The TTL output interface of the driver board generally contains three types of signals: RGB data signals, clock signals and control signals. The main control signals are: 1, DE enable signal 2, HS row synchronization signal, 3 column Sync signal

LVDS interface:

LVDS, or Low Voltage Differential Signaling, is a low voltage differential signal technology interface. A digital video signal transmission method developed to overcome the shortcomings of high power consumption and large EMI electromagnetic interference when transmitting broadband high bit rate data in TTL level mode. The LVDS output interface uses a very low voltage swing (about 350mV) to transmit data via differential on two PCB traces or a pair of balanced cables, that is, low-voltage differential signal transmission. Adopting LVDS output interface, can make the signal transmit at the speed of several hundred Mbit/s on the differential PCB line or balanced cable, because of adopting the low voltage and low current driving mode, therefore, realize low noise and low power consumption.

In the liquid crystal display, the LVDS interface circuit includes two parts, namely the LVDS output interface circuit on the main board side (LVDS transmitter) and the LVDS input interface circuit on the liquid crystal panel side (LVDS receiver). The LVDS transmitter converts the TTL signal into an LVDS signal, and then transmits the signal to the LVDS decoder IC of the LVDS receiver on the side of the LCD panel through the flexible cable (flat cable) between the driver board and the LCD panel. The LVDS receiver then serializes the The signal is converted into a TTL level parallel signal and sent to the LCD screen timing control and row and column drive circuit. In other words, TFT only recognizes TTL (RGB) signals.

EDP interface

eDP, Embedded DisplayPort is an internal digital interface based on the DisplayPort architecture and protocol. Suitable for tablet computers, notebooks, all-in-ones, and future new large-screen high-resolution mobile phones. At present, the signal transmission methods of laptop LCD screens can be divided into LVDS and eDP interfaces. Among them, eDP is a newer technology with more advantages than traditional LVDS interfaces.

HDMI interface

HDMI is currently the most mainstream high-definition interface, the full name is "high-definition multimedia interface", can support video and audio, if your monitor is equipped with audio, you can achieve audio transmission, such as LCD TV and some monitors that support audio. It supports high resolution, small interface, uncompressed audio streaming, and rich protocols.