Introduction to LVDS interface
Through the previous introduction, I believe everyone has a certain understanding of the TFT-LCD signal interface. Of course, in addition to the SPI, MCU, and RGB introduced earlier, the TFT-LCD signal interface also has various interface types such as LVDS, MIPI, eDP, HDMI, etc. ,
this issue introduces LVDS, an interface type that is widely used on the market. It mainly talks about the characteristics and signal composition of the LVDS interface.
The LVDS interface is the abbreviation of Low-Voltage Differential Signaling interface. Each data line is divided into two, namely the positive pole and the negative pole. The two low-voltage differential signal lines are combined into one data line, relying on multiple A combination of these data lines is used to realize data interaction between the CPU and LCD. There are many working modes of this interface signal. According to different numbers of data lines, the interface can be subdivided into two types: 1port and 2port. These two types of interface signals can be divided into two types: 1port and 2port. Divided into 3line and 4line modes, the pin definitions are usually divided into two types:
The first pin definition
Single-channel LVDS: RXINx-, RXINx+ (if it is 3line, it is RXIN0-~RXIN2-/RXIN0+~RXIN2+, if it is 4line, it is RXIN0-~RXIN3-/RXIN0+~RXIN3+) + (RXCLKIN-, RXCLKIN+) + power supply Line + RESET.
The second pin definition
Dual-channel LVDS (divided into ODD channel and EVEN channel, which is twice as many data lines as single-channel LVDS):
RXOINx-, RXOIN+ (if it is 3line, it is RXOIN0-~RXOIN2-/RXOIN0+~RXOIN2+, if it is 4line, it is RXOIN0-~RXOIN3-/RXOIN0+~RXOIN3+) + (RXOClockIN-, RXOClockIN+) +
RXEINx-, RXEIN+ (if it is 3line, it is RXEIN0-~RXEIN2-/RXEIN0+~RXEIN2+, if it is 4line, it is RXEIN0-~RXEIN3-/RXEIN0+~RXEIN3+) + (RXEClockIN-, RXEClockIN+) + power cord + RESET
This interface also has advantages and disadvantages. Because it uses a very low-amplitude differential line to transmit signals, the noise generated will be very small, the power consumed will be very small, and the transmission rate can be as high as thousands of Mbps. And because the polarity of the differential signals is opposite and can cancel each other’s electromagnetic fields, the interference they receive will also be very low.
Advantages: fast refresh speed, ability to play videos, strong anti-interference ability, low power consumption, etc.
However, because the vertical line synchronization signal needs to be set, corresponding circuits must be set up on the motherboard to cooperate with the software to control the frequency and data of the vertical line synchronization signal. Moreover, some main control ICs do not support the LVDS interface and need to use signal conversion. The chip is used for conversion, which increases the complexity of the motherboard circuit to a certain extent, and the software is also somewhat different. It is necessary to set the field line signal parameters, etc.
Disadvantages: takes up a lot of resources, requires additional signal conversion chips, relatively complex software, and cannot transmit instructions
Learn More：What is the function of LVDS?
