Applications
LVDS became popular in the mid 1990s. Before that, computer monitor resolutions were not large enough to need such fast data rates for graphics and video. However, in 1992 Apple Computer needed a method to transfer multiple streams of digital video without overloading the existing NuBus on the backplane. Apple and National Semiconductor (NSC) created QuickRing, which was the first integrated circuit using LVDS. QuickRing was a high speed auxiliary bus for video data to bypass the NuBus in Macintosh computers. The multimedia and supercomputer applications continued to expand because both needed to move large amounts of data over links several meters long (from a disk drive to a workstation for instance).
The first commercially successful application for LVDS was in notebook computers transmitting video data from graphics processing units to the flat panel displays using the Flat Panel Display Link by National Semiconductor. The first FPD-Link chipset reduced a 21-bit wide video interface plus the clock down to only 4 differential pairs (8 wires), which enabled it to easily fit through the hinge between the display and the notebook and take advantage of LVDS’s low-noise characteristics and fast data rate. FPD-Link became the de facto open standard for this notebook application in the late 1990s and is still the dominant display interface today in notebook and tablet computers. This is the reason IC vendors such as Texas Instruments, Maxim, Fairchild, and Thine produce their versions of the FPD-Link chipset.
The applications for LVDS expanded to flat panel displays for consumer TVs as screen resolutions and color depths increased. To serve this application, FPD-Link chipsets continued to increase the data-rate and the number of parallel LVDS channels to meet the internal TV requirement for transferring video data from the main video processor to the display-panel’s timing controller. FPD-Link (commonly called LVDS) became the de facto standard for this internal TV interconnect and remains the dominant interface for this application in 2012.
The next target application was transferring video streams through an external cable connection between a desktop computer and display, or a DVD player and a TV. NSC introduced higher performance follow-ons to FPD-Link called the LVDS Display Interface (LDI) and OpenLDI standards. These standards allow a maximum pixel clock of 112 MHz, which suffices for a display resolution of 1400 × 1050 (SXGA+) at 60 Hz refresh. A dual link can boost the maximum display resolution to 2048 × 1536 (QXGA) at 60 Hz. FPD-Link works with cable lengths up to about 5m, and LDI extends this to about 10m. However, Digital Visual Interface (DVI) using TMDS signals won the standards competition and became the standard for externally connecting desktop computers to monitors, and HDMI eventually became the standard for connecting digital video sources such as DVD players to flat panel displays in consumer applications.
Another successful LVDS application is Camera Link, which is a serial communication protocol designed for computer vision applications and based on the NSC chipset called Channel Link that uses LVDS. Camera Link standardizes video interfaces for scientific and industrial products including cameras, cables, and frame grabbers. The Automated Imaging Association (AIA) maintains and administers the standard because it is the industry’s global machine vision trade group.
More examples of LVDS used in computer buses are HyperTransport and FireWire, both of which trace their development back to the post-Futurebus work, which also led to SCI. In addition, LVDS is the physical layer signaling in SCSI standards (Ultra-2 SCSI and later) to allow higher data rates and longer cable lengths. Serial ATA, PCI Express, RapidIO, and SpaceWire use LVDS to allow high speed data transfer.
Intel and AMD published a press release in December 2010 stating they would no longer support the LVDS LCD-panel interface in their product lines by 2013. They are promoting Embedded DisplayPort and Internal DisplayPort as their preferred solution. However, the LVDS LCD-panel interface has proven to be the lowest cost method for moving streaming video from a video processing unit to a LCD-panel timing controller within a TV or notebook, and in February 2012 LCD TV and notebook manufacturers continue to introduce new products using the LVDS interface.
Read more about this topic: Low-voltage Differential Signaling