LCD interface knowledge

LCD interface knowledge

1. LVDS interface overview

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 large 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 differentially 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.

2. Composition of LVDS interface circuit

In the liquid crystal display, the LVDS interface circuit consists of 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.

Features of LCD

The reason for the high display quality is that each point of the LCD monitor keeps that color and brightness after receiving the signal, and emits constant light, unlike the cathode ray tube display (CRT) that needs to constantly refresh the bright spot. Therefore, the LCD display has high image quality and will never flicker, minimizing eye strain. Liquid crystals do not have electromagnetic radiation. The display material of traditional displays is phosphor. The electron beam hits the phosphor to display. The electron beam will generate strong electromagnetic radiation when it hits the phosphor. Although there are many display products currently dealing with radiation The problem has been dealt with more effectively to minimize the amount of radiation as much as possible, but it is difficult to completely eliminate it. Relatively speaking, liquid crystal displays have inherent advantages in preventing radiation, because there is no radiation at all. In terms of prevention of electromagnetic waves, liquid crystal displays also have their own unique advantages. It uses strict sealing technology to seal a small amount of electromagnetic waves from the drive circuit in the display. In order to dissipate heat, ordinary displays must make the internal circuit as much as possible. In contact with air, the electromagnetic waves generated by the internal circuit will "leak" to the outside. The viewing area of the liquid crystal is large and the application range is wide. For the display of the same size, the viewing area of the liquid crystal display is larger. The viewing area of a liquid crystal display is the same as its diagonal size.