Introduction and Application of DVI Signal Cable

Introduction and Application of DVI Signal Cable

What is DVI?
　　Nowadays, LCD monitors with DVI interfaces are very popular, and display cards equipped with the same interface are also common. This combination has led to the popularity of DVI, while the traditional VGA interface has gradually declined because it cannot fully match digital signals.

　　When it comes to DVI interfaces, many friends will think of the white D-type socket. Yes, this is the DVI interface, but it is different from the VGA interface. The DVI interface is divided into 3 categories and 5 standards. Each standard has its own scope of application. If it is not distinguished during use, it will affect the performance of the display device.

 
Definition of the DVI interface

　　A DVI display system includes a transmitter and a receiver. The transmitter is the source of the signal, which can be built into the graphics card chip or appear on the graphics card PCB in the form of an additional chip; the receiver is a circuit on the monitor that can receive digital signals, decode them and pass them to the digital display circuit. Through these two, the signal sent by the graphics card becomes the image on the monitor.

　　Compared with the traditional VGA signal, the LCD monitor using the DVI signal does not have phase problems and will not cause pixel jitter. In addition, after using the DVI signal, the monitor will not cause geometric distortion, which greatly improves the quality of the picture.

Different standards of DVI

　　Unlike the VGA interface, there are many standards for the DVI interface, which must be understood when using the monitor. As

　　can be seen from the chart below, DVI is divided into 5 standards. Among them, DVI-D and DVI-I are divided into two types: "dual channel" and "single channel". What we usually see are single-channel versions. The cost of the dual-channel version is very high, so only some professional equipment has it, and ordinary consumers rarely see it.

 
DVI-A is an analog transmission standard, which can be seen in late large-screen professional CRTs. However, since there is no essential difference between it and VGA and its performance is not high, DVI-A has actually been abandoned. As for the DFP interface, this is an early digital specification that has been abandoned.

Regarding the various characteristics of DVI signals:

Specification Signal Remarks DVI-I Dual-channel digital/analog convertible VGA DVI-I Single-channel digital/analog convertible VGA DVI-D Dual-channel digital non-convertible VGA DVI-D Single-channel digital non-convertible VGA DVI-A Analog Obsolete DFP Digital Obsolete VGA Analog - What is the difference between 18-pin and 24-pin?　　In the market, we often hear dealers describe DVI cables as 18+1 and 24+1 and 18+5 and 24+5. 　　Some people say that 18-pin is a simplified version and its performance is not as good as 24-pin; others say that some of the 24-pin are ground wires, and the effect is exactly the same as 18-pin. Which of these statements is correct? 　　In fact, the table above has revealed the details. 18 pins belong to single-channel DVI, and the transmission rate is only half of 24 pins, which is 165MHz. In terms of screen display, the resolution supported by single-channel DVI is exactly the same as that of dual-channel, but the refresh rate is only about half of that of dual-channel, which will cause a decline in display quality. Generally speaking, the maximum refresh rate of a single-channel DVI interface can only support 1920*1080*60hz or 1600*1200*60hz, that is, the normal display of existing 23-inch widescreen monitors and 20-inch ordinary ratio monitors. If it is higher, it will cause a decline in display effect. 　　At present, the LCD monitors we commonly use are still around 19-inch general screens and 20-inch widescreens. Few people really use large-screen monitors, so the 18-pin single-channel DVI interface is enough. If you use a large-screen LCD monitor, a 24-pin dual-channel DVI is a must. 

 
 
 
 
 
 
 

 

External TMDS chip, now this chip is mostly integrated into the display core.

　　In the past, display cards with DVI adopted the external TMDS solution, which was costly but effective. Now the display cores are all integrated with TMDS. Although the cost is reduced and the performance is improved on the surface, in fact, the graphics card has a serious problem of cutting corners, and the peripheral circuits are saved in a mess, and the output performance does not meet the requirements at all.

　　When evaluating monitors, the editor often finds that the refresh rate of some display cards cannot be increased when outputting 1600*1200 or 1920*1080 resolution. The problem is solved after replacing the display card. Afterwards, the analysis is that the display card is poorly made and the signal has problems, so the monitor cannot display normally.

 

This graphics card cannot meet the requirement of 60HZ refresh rate under 1920*1200.

　　Therefore, we have reason to suspect that some low-end cards will have problems when outputting the limit resolution. Therefore, it is recommended that friends who are equipped with good monitors buy regular brand products and do not buy inferior products for cheap.

　　As for the cables used, we think that the ones that come with the monitor can fully meet the requirements and there is no need to buy them separately. Especially for those who use small-screen monitors, there is no need to replace them. Professional monitors usually come with cables with good performance and there is no need to replace them.