LCD interface type introduction

LCD interface type introduction

LVDS

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 through 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.

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.

TTL

1. Overview of TTL interface

TTL (Transistor Transistor Logic) is transistor-transistor logic, and TTL level signals are generated by TTL devices. TTL devices are a major category of digital integrated circuits. They are manufactured using bipolar technology and have the characteristics of high speed, low power consumption and many varieties.

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 at the driver board side and the LCD panel side of the liquid crystal display, but the TTL data signal output by the main control chip of the driver board is passed through the cable. Directly transmit to the input interface of the LCD panel. Due to the high signal voltage of the TTL interface, multiple 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 (under 15in) or low-resolution LCD panels. The highest pixel clock of TTL is only 28MHz. TTL is the only signal that TFT-LCD can recognize when the signal is signal. Early digital processing chips are all TTL, that is, RGB is directly output to TFT-LCD.

Single channel 6bit TTL output interface

For the 6bit single-channel TTL output interface, there are 18 RGB data lines, which are 6 R0～R5 red primary color data, 6 G0～G5 green primary color data, and B0～B5 blue primary color data, a total of 3*6=18 Article. Since the primary color RGB data is 18bit, it is also called 18bit or 18bitTTL interface.

Single channel 8bit TTL output interface

For the 8-bit single-channel TTI, output interface, there are 24 RGB data lines, 8 R0～R7 red primary color data, 8 B0～B7 green primary color data, 8 BO～B7 blue primary color data, total 3*8= 24 articles. Since the primary color RGB data is 24bit, it is also called 24-bit or 24bitTTL interface.

Dual-channel 6bit TTL output interface

For the 6bit dual TTL output interface, there are 36 RGB data lines, 18 odd RGB data lines, 18 even RGB data lines, 3*6*3=36. Since the primary color ROB data is 36bit, it is also called 36bit or 36bitTTL interface.

Dual channel 8bit TTL output interface

For the 8-bit dual TTL output interface, there are 48 RGB data lines, 24 odd RGB data lines, 24 even RGB data lines, 3*8*2=48. Since the primary color RGB data is 48bit, it is also called 48bit or 48bitTTL interface.