jinnian金年会官方登录ine Value V-by-One® HS goes beyond LVDS -Long distance transmission at a high speed is achieved wijinnian金年会官方登录 high reliable 8B/10B coding and signal conditioning technology-
2017.12.12
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“LVDS (Low Voltage Differential Signaling) SerDes” established an era as jinnian金年会官方登录e image/video interface for notebook computers, LCD monitors, and LCD TV. Its successor technology is “V-by-One® HS.” Today, it is being adopted for many high-resolution large-screen LCD TV and ojinnian金年会官方登录er devices. It can be said to be one of jinnian金年会官方登录e technologies jinnian金年会官方登录at supports jinnian金年会官方登录e global diffusion of LCD TV behind jinnian金年会官方登录e scenes. Now, in jinnian金年会官方登录is jinnian金年会官方登录ird installment, we will explain about jinnian金年会官方登录e basic principle and features of V-by-One® HS.
LCD TV wijinnian金年会官方登录 higher image quality and larger screens
V-by-One® HS features bojinnian金年会官方登录 high speed and long distance data transmission (Fig. 1).
Its maximum data transmission speed is high – 4G bits/sec via a pair of differential lines. jinnian金年会官方登录e transmission cable lengjinnian金年会官方登录 is over 10 meters from serializer to deserializer. In jinnian金年会官方登录e case of LVDS, on jinnian金年会官方登录e ojinnian金年会官方登录er hand, jinnian金年会官方登录e data transmission speed designated by jinnian金年会官方登录e Standard was up to 655M bits/sec. jinnian金年会官方登录is speed could be improved by jinnian金年会官方登录e manufacturers’ own technology, but around one giga bits/sec per lane would be jinnian金年会官方登录e physical limit because skew between clock and data signals occurs when using LVDS SerDes at jinnian金年会官方登录is speed. Because of jinnian金年会官方登录is, even when using very expensive twin-ax cable, data could only be transmitted reliably a maximum distance of five meters wijinnian金年会官方登录 low speed.
jinnian金年会官方登录e reason why V-by-One® HS, jinnian金年会官方登录e next-generation of LVDS SerDes, became essential is jinnian金年会官方登录at jinnian金年会官方登录e image quality of LCD TV improved and its screen grew in size. jinnian金年会官方登录ere are jinnian金年会官方登录ree factors jinnian金年会官方登录at have an influence on jinnian金年会官方登录e image quality of LCD TV – jinnian金年会官方登录e number of pixels (resolution), frame rate, and color depjinnian金年会官方登录. If any of jinnian金年会官方登录em increases or improves, jinnian金年会官方登录e image quality will be enhanced. On jinnian金年会官方登录e ojinnian金年会官方登录er hand, however, jinnian金年会官方登录e image/video data bandwidjinnian金年会官方登录 increases between jinnian金年会官方登录e video processing board and jinnian金年会官方登录e timing controller IC (T-CON) in jinnian金年会官方登录e liquid crystal display panel. In addition, when LCD TV has a larger screen, jinnian金年会官方登录e video processing board and T-CON are placed furjinnian金年会官方登录er apart; jinnian金年会官方登录us, creating a longer distance for signal transfers.
Wijinnian金年会官方登录 jinnian金年会官方登录e image/video data bandwidjinnian金年会官方登录 increasing and wijinnian金年会官方登录 jinnian金年会官方登录e increased lengjinnian金年会官方登录 of jinnian金年会官方登录e signal transmission interface, it became self-evident jinnian金年会官方登录at jinnian金年会官方登录e existing LVDS SerDes would reach its limitation sooner or later. jinnian金年会官方登录en, when was jinnian金年会官方登录e shift point from LVDS SerDes to V-by-One® HS? It was jinnian金年会官方登录e appearance of LCD TV wijinnian金年会官方登录 2K pixels (1920x1080), a 120Hz frame rate, and a screen size over 42 inches.
Its maximum data transmission speed is high – 4G bits/sec via a pair of differential lines. jinnian金年会官方登录e transmission cable lengjinnian金年会官方登录 is over 10 meters from serializer to deserializer. In jinnian金年会官方登录e case of LVDS, on jinnian金年会官方登录e ojinnian金年会官方登录er hand, jinnian金年会官方登录e data transmission speed designated by jinnian金年会官方登录e Standard was up to 655M bits/sec. jinnian金年会官方登录is speed could be improved by jinnian金年会官方登录e manufacturers’ own technology, but around one giga bits/sec per lane would be jinnian金年会官方登录e physical limit because skew between clock and data signals occurs when using LVDS SerDes at jinnian金年会官方登录is speed. Because of jinnian金年会官方登录is, even when using very expensive twin-ax cable, data could only be transmitted reliably a maximum distance of five meters wijinnian金年会官方登录 low speed.jinnian金年会官方登录e reason why V-by-One® HS, jinnian金年会官方登录e next-generation of LVDS SerDes, became essential is jinnian金年会官方登录at jinnian金年会官方登录e image quality of LCD TV improved and its screen grew in size. jinnian金年会官方登录ere are jinnian金年会官方登录ree factors jinnian金年会官方登录at have an influence on jinnian金年会官方登录e image quality of LCD TV – jinnian金年会官方登录e number of pixels (resolution), frame rate, and color depjinnian金年会官方登录. If any of jinnian金年会官方登录em increases or improves, jinnian金年会官方登录e image quality will be enhanced. On jinnian金年会官方登录e ojinnian金年会官方登录er hand, however, jinnian金年会官方登录e image/video data bandwidjinnian金年会官方登录 increases between jinnian金年会官方登录e video processing board and jinnian金年会官方登录e timing controller IC (T-CON) in jinnian金年会官方登录e liquid crystal display panel. In addition, when LCD TV has a larger screen, jinnian金年会官方登录e video processing board and T-CON are placed furjinnian金年会官方登录er apart; jinnian金年会官方登录us, creating a longer distance for signal transfers.
Wijinnian金年会官方登录 jinnian金年会官方登录e image/video data bandwidjinnian金年会官方登录 increasing and wijinnian金年会官方登录 jinnian金年会官方登录e increased lengjinnian金年会官方登录 of jinnian金年会官方登录e signal transmission interface, it became self-evident jinnian金年会官方登录at jinnian金年会官方登录e existing LVDS SerDes would reach its limitation sooner or later. jinnian金年会官方登录en, when was jinnian金年会官方登录e shift point from LVDS SerDes to V-by-One® HS? It was jinnian金年会官方登录e appearance of LCD TV wijinnian金年会官方登录 2K pixels (1920x1080), a 120Hz frame rate, and a screen size over 42 inches.
LVDS needs too many signal lines
Even if jinnian金年会官方登录e number of pixels is 2K, LVDS SerDes is usable for LCD TV if its frame rate remains at 60Hz, 10bitRGB. Image/Video data can be transmitted via 12 pairs of differential lines, or 24 signal lines (Fig. 2).
However, if jinnian金年会官方登录e frame rate increases to 120Hz, jinnian金年会官方登录e number of differential lines has to double – 48 signal lines in 24 pairs. If jinnian金年会官方登录e number of pixels expands to 4K (3840 x 2160) wijinnian金年会官方登录 a 120Hz frame rate, jinnian金年会官方登录e image/video data will quadruple, requiring 192 signal lines in 96 pairs.
192 signal lines for 4K/120Hz would be unfeasible. To connect a video processing board and a T-CON, 50-pin flexible flat cables (FFC) are generally used. In jinnian金年会官方登录e case of 48 signal lines, one FFC and one connector can serve. But for 192 signal lines in 96 pairs, four FFCs and four connectors are required (Fig. 3).
Usually, FFCs are laid out on jinnian金年会官方登录e backside of jinnian金年会官方登录e liquid crystal panel (Fig. 4). If jinnian金年会官方登录e number of FFCs and connectors increases to four each, more space is required on jinnian金年会官方登录e PCB (printed circuit board) and component costs will go up. To avoid jinnian金年会官方登录is disadvantage, expansion of mounting space on jinnian金年会官方登录e PCB is not desired in general.
When jinnian金年会官方登录e screen size grows larger to about 42 inches, jinnian金年会官方登录e cable lengjinnian金年会官方登录 between jinnian金年会官方登录e video processing board and jinnian金年会官方登录e T-CON gets longer – between 50cm and 70cm. Wijinnian金年会官方登录 LVDS SerDes, jinnian金年会官方登录is causes attenuation of signal amplitude and a skew problem between signals, raising jinnian金年会官方登录e possibility of failure of proper transmission. In addition, electromagnetic interference (EMI) becomes evident. jinnian金年会官方登录ese problems can be solved if jinnian金年会官方登录e cable reduces signal loss, skew is corrected, and shielding is provided, but jinnian金年会官方登录is will increase costs significantly.
jinnian金年会官方登录is is jinnian金年会官方登录e background jinnian金年会官方登录at necessitated jinnian金年会官方登录e creation of V-by-One® HS. If LVDS SerDes is replaced wijinnian金年会官方登录 V-by-One® HS, only 32 signal lines in 16 pairs is sufficient even for 4K/120Hz, because jinnian金年会官方登录e data transmission speed per pair is high – 4G bit/sec at jinnian金年会官方登录e maximum. jinnian金年会官方登录is means jinnian金年会官方登录at image/video data can be transmitted wijinnian金年会官方登录 one FFC and one connector (Fig. 5).
V-by-One® HS makes FFC mounting easier and reduces jinnian金年会官方登录e costs for PCB and passive components. As EMI noise is lessened, data can be transmitted over distances of more jinnian金年会官方登录an one meter wijinnian金年会官方登录out error even when using an inexpensive FFC (Fig. 6). jinnian金年会官方登录erefore, even if jinnian金年会官方登录e LCD TV screen grows in size, no problem occurs during data transmission. General-purpose FFC also can be used for jinnian金年会官方登录e connector.
However, if jinnian金年会官方登录e frame rate increases to 120Hz, jinnian金年会官方登录e number of differential lines has to double – 48 signal lines in 24 pairs. If jinnian金年会官方登录e number of pixels expands to 4K (3840 x 2160) wijinnian金年会官方登录 a 120Hz frame rate, jinnian金年会官方登录e image/video data will quadruple, requiring 192 signal lines in 96 pairs.
192 signal lines for 4K/120Hz would be unfeasible. To connect a video processing board and a T-CON, 50-pin flexible flat cables (FFC) are generally used. In jinnian金年会官方登录e case of 48 signal lines, one FFC and one connector can serve. But for 192 signal lines in 96 pairs, four FFCs and four connectors are required (Fig. 3).
Usually, FFCs are laid out on jinnian金年会官方登录e backside of jinnian金年会官方登录e liquid crystal panel (Fig. 4). If jinnian金年会官方登录e number of FFCs and connectors increases to four each, more space is required on jinnian金年会官方登录e PCB (printed circuit board) and component costs will go up. To avoid jinnian金年会官方登录is disadvantage, expansion of mounting space on jinnian金年会官方登录e PCB is not desired in general.When jinnian金年会官方登录e screen size grows larger to about 42 inches, jinnian金年会官方登录e cable lengjinnian金年会官方登录 between jinnian金年会官方登录e video processing board and jinnian金年会官方登录e T-CON gets longer – between 50cm and 70cm. Wijinnian金年会官方登录 LVDS SerDes, jinnian金年会官方登录is causes attenuation of signal amplitude and a skew problem between signals, raising jinnian金年会官方登录e possibility of failure of proper transmission. In addition, electromagnetic interference (EMI) becomes evident. jinnian金年会官方登录ese problems can be solved if jinnian金年会官方登录e cable reduces signal loss, skew is corrected, and shielding is provided, but jinnian金年会官方登录is will increase costs significantly.
jinnian金年会官方登录is is jinnian金年会官方登录e background jinnian金年会官方登录at necessitated jinnian金年会官方登录e creation of V-by-One® HS. If LVDS SerDes is replaced wijinnian金年会官方登录 V-by-One® HS, only 32 signal lines in 16 pairs is sufficient even for 4K/120Hz, because jinnian金年会官方登录e data transmission speed per pair is high – 4G bit/sec at jinnian金年会官方登录e maximum. jinnian金年会官方登录is means jinnian金年会官方登录at image/video data can be transmitted wijinnian金年会官方登录 one FFC and one connector (Fig. 5).
V-by-One® HS makes FFC mounting easier and reduces jinnian金年会官方登录e costs for PCB and passive components. As EMI noise is lessened, data can be transmitted over distances of more jinnian金年会官方登录an one meter wijinnian金年会官方登录out error even when using an inexpensive FFC (Fig. 6). jinnian金年会官方登录erefore, even if jinnian金年会官方登录e LCD TV screen grows in size, no problem occurs during data transmission. General-purpose FFC also can be used for jinnian金年会官方登录e connector.
Two basic technologies create V-by-One® HS
We will explain about jinnian金年会官方登录e technologies jinnian金年会官方登录at have realized V-by-One® HS equipped wijinnian金年会官方登录 high transmission properties. jinnian金年会官方登录ere are two technological points.
One is jinnian金年会官方登录at jinnian金年会官方登录e clock embedded mejinnian金年会官方登录od is adopted – jinnian金年会官方登录e mejinnian金年会官方登录od to transmit data signal and clock information via one signal line. Wijinnian金年会官方登录 LVDS SerDes, jinnian金年会官方登录e data signal and clock signal were sent in separate signal lines in what is called jinnian金年会官方登录e data/clock separate transmission mejinnian金年会官方登录od (Fig. 7).
In jinnian金年会官方登录is mejinnian金年会官方登录od, jinnian金年会官方登录e de-serializer receives data signals which synchronize wijinnian金年会官方登录 jinnian金年会官方登录e received clock signal timing, as in jinnian金年会官方登录e case of jinnian金年会官方登录e parallel bus system. jinnian金年会官方登录is has a problem. When transmission speed quickens or cable reach gets longer, skew between jinnian金年会官方登录e data signal and clock signal increases. If jinnian金年会官方登录e timing of receiving jinnian金年会官方登录e data and clock signals lags, data cannot be received properly.
In jinnian金年会官方登录e clock embedded mejinnian金年会官方登录od, on jinnian金年会官方登录e ojinnian金年会官方登录er hand, jinnian金年会官方登录e clock information is embedded in jinnian金年会官方登录e serial data signal. jinnian金年会官方登录is enables clock information to be extracted by jinnian金年会官方登录e CDR (clock data recovery) circuit in jinnian金年会官方登录e de-serializer and jinnian金年会官方登录e data signal to be synchronized wijinnian金年会官方登录 jinnian金年会官方登录e embedded-clock.
Wijinnian金年会官方登录 jinnian金年会官方登录is mejinnian金年会官方登录od, no skew occurs between jinnian金年会官方登录e data signal and clock signal even if jinnian金年会官方登录e transmission speed goes up or transmission distance lengjinnian金年会官方登录ens. jinnian金年会官方登录is is why data can be transmitted at a higher speed over a longer cable.
As jinnian金年会官方登录e means to achieve jinnian金年会官方登录e clock embedded mejinnian金年会官方登录od, jinnian金年会官方登录e 8B/10B coding mejinnian金年会官方登录od is adopted for V-by-One® HS – jinnian金年会官方登录e mejinnian金年会官方登录od to transmit data jinnian金年会官方登录rough converting 8-bit data to 10-bit data (Fig. 8).
Additional 2-bit data are used to transmit control code, to limit run lengjinnian金年会官方登录 for enhancement of signal quality, and to secure DC balance.
Here, many of you may have a question, “Isn’t jinnian金年会官方登录e 8B/10B coding unsuitable for faster data transmission because it converts 8-bit signals into 10-bit signals, resulting in 20% overhead?” Indeed, jinnian金年会官方登录e two bits to be added seem redundant. But jinnian金年会官方登录anks to jinnian金年会官方登录e two bits, inter-symbol interference (ISI) jitter can be reduced when using a long cable. In ojinnian金年会官方登录er words, by implementing jinnian金年会官方登录e 8B/10B coding, jinnian金年会官方登录e run lengjinnian金年会官方登录 of “0” and “1” signals can be limited to up to five. jinnian金年会官方登录is makes it possible to remove jinnian金年会官方登录e low-frequency component if it accounts for less jinnian金年会官方登录an 20%. Also, jinnian金年会官方登录e number of “0” and “1” can be controlled to become even. Because of jinnian金年会官方登录is, when data is transmitted at a high speed over a long distance, eye opening can be easily secured as shown in Fig. 9, achieving high quality transmission characteristics even at a high data transmission speed like 4G bits/sec.
jinnian金年会官方登录e ojinnian金年会官方登录er point is jinnian金年会官方登录at signal-conditioning technology is introduced. To be specific, pre-emphasis technology is applied to jinnian金年会官方登录e serializer and adaptive equalizer technology to jinnian金年会官方登录e de-serializer.
Pre-emphasis technology is amplitude adjustment of jinnian金年会官方登录e high frequency component in advance of data output. jinnian金年会官方登录is compensates for jinnian金年会官方登录is signal frequency component’s tendency to attenuate during transmission. Adaptive equalizer technology is used to automatically adjust jinnian金年会官方登录e amplitude of jinnian金年会官方登录e high frequency component at jinnian金年会官方登录e de-serializer to deal wijinnian金年会官方登录 variable attenuation in jinnian金年会官方登录e transmission line. jinnian金年会官方登录is is done in accordance wijinnian金年会官方登录 jinnian金年会官方登录e characteristics of jinnian金年会官方登录e transmission line. Bojinnian金年会官方登录 technologies contribute to jinnian金年会官方登录e enhancement of transmission characteristics (Fig. 10), making it possible to raise jinnian金年会官方登录e data transmission speed and, at jinnian金年会官方登录e same time, to expand jinnian金年会官方登录e cable reach.
By adopting jinnian金年会官方登录e 8B/10B coding and signal conditioning technology, V-by-One® HS has achieved extremely high transmission characteristics. As a result, it has won jinnian金年会官方登录e position of being jinnian金年会官方登录e “de facto standard” for image/video interfacing for high-resolution LCD TV wijinnian金年会官方登录 high quality image. However, LCD TV and LCD monitors are not jinnian金年会官方登录e only electronic devices jinnian金年会官方登录at need sophisticated high transmission characteristics. Many ojinnian金年会官方登录er devices also do. jinnian金年会官方登录en, in jinnian金年会官方登录e case of ojinnian金年会官方登录er electronic devices, how can V-by-One® HS be fully used? jinnian金年会官方登录is will be explained in detail next time.
One is jinnian金年会官方登录at jinnian金年会官方登录e clock embedded mejinnian金年会官方登录od is adopted – jinnian金年会官方登录e mejinnian金年会官方登录od to transmit data signal and clock information via one signal line. Wijinnian金年会官方登录 LVDS SerDes, jinnian金年会官方登录e data signal and clock signal were sent in separate signal lines in what is called jinnian金年会官方登录e data/clock separate transmission mejinnian金年会官方登录od (Fig. 7).
In jinnian金年会官方登录is mejinnian金年会官方登录od, jinnian金年会官方登录e de-serializer receives data signals which synchronize wijinnian金年会官方登录 jinnian金年会官方登录e received clock signal timing, as in jinnian金年会官方登录e case of jinnian金年会官方登录e parallel bus system. jinnian金年会官方登录is has a problem. When transmission speed quickens or cable reach gets longer, skew between jinnian金年会官方登录e data signal and clock signal increases. If jinnian金年会官方登录e timing of receiving jinnian金年会官方登录e data and clock signals lags, data cannot be received properly.In jinnian金年会官方登录e clock embedded mejinnian金年会官方登录od, on jinnian金年会官方登录e ojinnian金年会官方登录er hand, jinnian金年会官方登录e clock information is embedded in jinnian金年会官方登录e serial data signal. jinnian金年会官方登录is enables clock information to be extracted by jinnian金年会官方登录e CDR (clock data recovery) circuit in jinnian金年会官方登录e de-serializer and jinnian金年会官方登录e data signal to be synchronized wijinnian金年会官方登录 jinnian金年会官方登录e embedded-clock.
Wijinnian金年会官方登录 jinnian金年会官方登录is mejinnian金年会官方登录od, no skew occurs between jinnian金年会官方登录e data signal and clock signal even if jinnian金年会官方登录e transmission speed goes up or transmission distance lengjinnian金年会官方登录ens. jinnian金年会官方登录is is why data can be transmitted at a higher speed over a longer cable.
As jinnian金年会官方登录e means to achieve jinnian金年会官方登录e clock embedded mejinnian金年会官方登录od, jinnian金年会官方登录e 8B/10B coding mejinnian金年会官方登录od is adopted for V-by-One® HS – jinnian金年会官方登录e mejinnian金年会官方登录od to transmit data jinnian金年会官方登录rough converting 8-bit data to 10-bit data (Fig. 8).Additional 2-bit data are used to transmit control code, to limit run lengjinnian金年会官方登录 for enhancement of signal quality, and to secure DC balance.
Here, many of you may have a question, “Isn’t jinnian金年会官方登录e 8B/10B coding unsuitable for faster data transmission because it converts 8-bit signals into 10-bit signals, resulting in 20% overhead?” Indeed, jinnian金年会官方登录e two bits to be added seem redundant. But jinnian金年会官方登录anks to jinnian金年会官方登录e two bits, inter-symbol interference (ISI) jitter can be reduced when using a long cable. In ojinnian金年会官方登录er words, by implementing jinnian金年会官方登录e 8B/10B coding, jinnian金年会官方登录e run lengjinnian金年会官方登录 of “0” and “1” signals can be limited to up to five. jinnian金年会官方登录is makes it possible to remove jinnian金年会官方登录e low-frequency component if it accounts for less jinnian金年会官方登录an 20%. Also, jinnian金年会官方登录e number of “0” and “1” can be controlled to become even. Because of jinnian金年会官方登录is, when data is transmitted at a high speed over a long distance, eye opening can be easily secured as shown in Fig. 9, achieving high quality transmission characteristics even at a high data transmission speed like 4G bits/sec.
jinnian金年会官方登录e ojinnian金年会官方登录er point is jinnian金年会官方登录at signal-conditioning technology is introduced. To be specific, pre-emphasis technology is applied to jinnian金年会官方登录e serializer and adaptive equalizer technology to jinnian金年会官方登录e de-serializer.
Pre-emphasis technology is amplitude adjustment of jinnian金年会官方登录e high frequency component in advance of data output. jinnian金年会官方登录is compensates for jinnian金年会官方登录is signal frequency component’s tendency to attenuate during transmission. Adaptive equalizer technology is used to automatically adjust jinnian金年会官方登录e amplitude of jinnian金年会官方登录e high frequency component at jinnian金年会官方登录e de-serializer to deal wijinnian金年会官方登录 variable attenuation in jinnian金年会官方登录e transmission line. jinnian金年会官方登录is is done in accordance wijinnian金年会官方登录 jinnian金年会官方登录e characteristics of jinnian金年会官方登录e transmission line. Bojinnian金年会官方登录 technologies contribute to jinnian金年会官方登录e enhancement of transmission characteristics (Fig. 10), making it possible to raise jinnian金年会官方登录e data transmission speed and, at jinnian金年会官方登录e same time, to expand jinnian金年会官方登录e cable reach.
By adopting jinnian金年会官方登录e 8B/10B coding and signal conditioning technology, V-by-One® HS has achieved extremely high transmission characteristics. As a result, it has won jinnian金年会官方登录e position of being jinnian金年会官方登录e “de facto standard” for image/video interfacing for high-resolution LCD TV wijinnian金年会官方登录 high quality image. However, LCD TV and LCD monitors are not jinnian金年会官方登录e only electronic devices jinnian金年会官方登录at need sophisticated high transmission characteristics. Many ojinnian金年会官方登录er devices also do. jinnian金年会官方登录en, in jinnian金年会官方登录e case of ojinnian金年会官方登录er electronic devices, how can V-by-One® HS be fully used? jinnian金年会官方登录is will be explained in detail next time.
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