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52-477: LVD may refer to: Low-voltage differential signaling , an electrical signaling method that can run at very high speeds over inexpensive twisted-pair copper cables. Low Voltage Directive , European directive 2006/95/EC for the safety of electrical equipment sold within the European Union . Low-voltage detect is a microcontroller technology that asserts

104-429: A decoupling capacitor is a capacitor used to decouple (i.e. prevent electrical energy from transferring to) one part of a circuit from another. Noise caused by other circuit elements is shunted through the capacitor, reducing its effect on the rest of the circuit. For higher frequencies, an alternative name is bypass capacitor as it is used to bypass the power supply or other high- impedance component of

156-517: 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

208-472: A RESET when Vcc falls below Vref. Large Volume Detector , particle physics experiment situated in Italy. Liquid vapor display , display technology. Ludwig Von Drake , Disney character Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title LVD . If an internal link led you here, you may wish to change the link to point directly to

260-601: A TV or notebook, and in February 2018 LCD TV and notebook manufacturers continue to introduce new products using the LVDS interface. LVDS was originally introduced as a 3.3 V standard. Scalable low voltage signaling ( SLVS ) has a lower common-mode voltage of 200 mV and a reduced p-p swing, but is otherwise the same as LVDS. LVDS works in both parallel and serial data transmission . In parallel transmissions multiple data differential pairs carry several signals at once including

312-592: A capacitor to circuit ground instead of to the harder path of the decoupled circuit, but DC cannot go through the capacitor and continues to the decoupled circuit. Another kind of decoupling is stopping a portion of a circuit from being affected by switching that occurs in another portion of the circuit. Switching in subcircuit A may cause fluctuations in the power supply or other electrical lines, but you do not want subcircuit B, which has nothing to do with that switching, to be affected. A decoupling capacitor can decouple subcircuits A and B so that B doesn't see any effects of

364-400: A circuit. Active devices of an electronic system (e.g. transistors , integrated circuits , vacuum tubes ) are connected to their power supplies through conductors with finite resistance and inductance . If the current drawn by an active device changes, the voltage drop from the power supply to the device will also change due to these impedances . If several active devices share

416-421: A clock signal to synchronize the data. In serial communications, multiple single-ended signals are serialized into a single differential pair with a data rate equal to that of all the combined single-ended channels. For example, a 7-bit wide parallel bus serialized into a single pair that will operate at 7 times the data rate of one single-ended channel. The devices for converting between serial and parallel data are

468-414: A common path to the power supply, changes in the current drawn by one element may produce voltage changes large enough to affect the operation of others – voltage spikes or ground bounce , for example – so the change of state of one device is coupled to others through the common impedance to the power supply. A decoupling capacitor provides a bypass path for transient currents, instead of flowing through

520-429: A corresponding network controller and, if necessary resources for data compression. Since for many applications a full function network is not required throughout the video architecture and for some compounds, data compression is not feasible due to image quality loss and additional latency, bus-oriented video transmission technologies are currently only partially attractive. Decoupling capacitor In electronics ,

572-448: A current appears abruptly during switching. The low common-mode voltage (the average of the voltages on the two wires) of about 1.2 V allows using LVDS with a wide range of integrated circuits with power supply voltages down to 2.5 V or lower. In addition, there are variations of LVDS that use a lower common mode voltage. One example is sub-LVDS (introduced by Nokia in 2004) that uses 0.9 V typical common mode voltage. Another

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624-462: A decoupling capacitor close to each logic IC connected from each power supply connection to a nearby ground. These capacitors decouple every IC from every other IC in terms of supply voltage dips. These capacitors are often placed at each power source as well as at each analog component in order to ensure that the supplies are as steady as possible. Otherwise, an analog component with a poor power supply rejection ratio (PSRR) will copy fluctuations in

676-408: A high-power amplifier stage with a low-level pre-amplifier coupled to it. Care must be taken in the layout of circuit conductors so that heavy current at one stage does not produce power supply voltage drops that affect other stages. This may require re-routing printed circuit board traces to segregate circuits, or the use of a ground plane to improve the stability of power supply. A bypass capacitor

728-422: 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 5 m, and LDI extends this to about 10 m. However, Digital Visual Interface (DVI) using TMDS over CML signals won the standards competition and became

780-596: 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

832-521: 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

884-399: A single differential pair of serial data is not fast enough there are techniques for grouping serial data channels in parallel and adding a parallel clock channel for synchronization. This is the technique used by FPD-Link. Other examples of parallel LVDS using multiple LVDS pairs and a parallel clock to synchronize are Channel Link and HyperTransport . There is also the technique to increase

936-434: A start-bit and stop-bit to guarantee bit transitions at regular intervals to mimic a clock signal. Another method is 8b/10b encoding. LVDS does not specify a bit encoding scheme because it is a physical layer standard only. LVDS accommodates any user-specified encoding scheme for sending and receiving data across an LVDS link, including 8b/10b encoded data. An 8b/10b encoding scheme embeds the clock signal information and has

988-503: Is Scalable Low Voltage Signaling for 400 mV (SLVS-400) specified in JEDEC JESD8-13 October 2001 where the power supply can be as low as 800 mV and common mode voltage is about 400 mV. The low differential voltage, about 350 mV, causes LVDS to consume very little power compared to other signaling technologies. At 2.5 V supply voltage the power to drive 3.5 mA becomes 8.75 mW, compared to

1040-674: Is large enough, sufficient current is supplied to maintain an acceptable range of voltage drop. The capacitor stores a small amount of energy that can compensate for the voltage drop in the power supply conductors to the capacitor. To reduce undesired parasitic equivalent series inductance , small and large capacitors are often placed in parallel , adjacent to individual integrated circuits (see § Placement ). In digital circuits, decoupling capacitors also help prevent radiation of electromagnetic interference from relatively long circuit traces due to rapidly changing power supply currents. Decoupling capacitors alone may not suffice in such cases as

1092-417: Is much lower compared to the inductance between the loads and the output of the power supply. To decouple other subcircuits from the effect of the sudden current demand, a decoupling capacitor can be placed in parallel with the subcircuit, across its supply voltage lines. When switching occurs in the subcircuit, the capacitor supplies the transient current. Ideally, by the time the capacitor runs out of charge,

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1144-428: Is often used to decouple a subcircuit from AC signals or voltage spikes on a power supply or other line. A bypass capacitor can shunt energy from those signals, or transients, past the subcircuit to be decoupled, right to the return path. For a power supply line, a bypass capacitor from the supply voltage line to the power supply return (neutral) would be used. High frequencies and transient currents can flow through

1196-643: The IEEE 1596.3 1995 standard. The SCI committee designed LVDS for interconnecting multiprocessing systems with a high-speed low-power interface to replace positive emitter-coupled logic (PECL). The ANSI / TIA / EIA -644-A (published in 2001) standard defines LVDS. This standard originally recommended a maximum data rate of 655 Mbit/s over twisted-pair copper wire, but data rates from 1 to 3 Gbit/s are common today on high-quality transmission mediums. Today, technologies for broadband digital video signal transmission such as LVDS are also used in vehicles, in which

1248-630: The 90 mW dissipated by the load resistor for an RS-422 signal. Logic levels: LVDS is not the only low-power differential signaling system in use, others include the Fairchild Current Transfer Logic serial I/O. In 1994, National Semiconductor introduced LVDS, which later became a de facto standard for high-speed data transfer. 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

1300-501: 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

1352-405: The FPD-Link parallel pairs are carrying serialized data, but use a parallel clock to recover and synchronize the data. Serial data communications can also embed the clock within the serial data stream. This eliminates the need for a parallel clock to synchronize the data. There are multiple methods for embedding a clock into a data stream. One method is inserting 2 extra bits into the data stream as

1404-450: The added benefit of DC balance. DC balance is necessary for AC-coupled transmission paths (such as capacitive or transformer-coupled paths). There are also DC-balance encoding methods for the start bit/stop bit embedded clock, which usually include a data scrambling technique. The key point in LVDS is the physical layer signaling to transport bits across wires. It is compatible with almost all data encoding and clock embedding techniques. When

1456-540: The automobile for linking cameras, displays, and control devices. The uncompressed video data has some advantages for certain applications. Serial communication protocols now allow the transfer of data rates in the range of 3 to 4 Gbit/s and thus the control of displays with up to full HD resolution. The integration of the serializer and deserializer components in the control unit due to low demands on additional hardware and software simple and inexpensive. In contrast, require bus solutions for video transmission connection to

1508-555: The backplane to each of the computing module boards in the system. MLVDS has two types of receivers. Type-1 is compatible with LVDS and uses a +/− 50 mV threshold. Type-2 receivers allow Wired-Or signaling with M-LVDS devices. For M-LVDS: The present form of LVDS was preceded by an earlier standard initiated in Scalable Coherent Interface (SCI). SCI-LVDS was a subset of the SCI family of standards and specified in

1560-398: The common impedance. The decoupling capacitor works as the device’s local energy storage . The capacitor is placed between the power line and the ground to the circuit the current is to be provided. According to the capacitor current–voltage relation a voltage drop between a power line and the ground results in a current drawn out from the capacitor to the circuit. When capacitance C

1612-567: The common-mode noise impacts both pairs equally, resulting in no relative voltage difference between them. The fact that the LVDS transmitter consumes a constant current also places much less demand on the power supply decoupling and thus produces less interference in the power and ground lines of the transmitting circuit. This reduces or eliminates phenomena such as ground bounce which are typically seen in terminated single-ended transmission lines where high and low logic levels consume different currents, or in non-terminated transmission lines where

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1664-399: The conductor between the capacitor and the device, the more inductance is present. Since capacitors differ in their high-frequency characteristics, decoupling ideally involves the use of a combination of capacitors. For example in logic circuits, a common arrangement is ~100 nF ceramic per logic IC (multiple ones for complex ICs), combined with electrolytic or tantalum capacitor (s) up to

1716-432: The data throughput by grouping multiple LVDS-with-embedded-clock data channels together. However, this is not parallel LVDS because there is no parallel clock and each channel has its own clock information. An example of this technique is PCI Express where 2, 4, or 8 8b/10b encoded serial channels carry application data from source to destination. In this case the destination must employ a data synchronization method to align

1768-504: 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

1820-416: The differential transmission line to maintain the signal integrity. Double termination is necessary because it is possible to have one or more transmitters in the center of the bus driving signals toward receivers in both directions. The difference from standard LVDS transmitters was increasing the current output in order to drive the multiple termination resistors. In addition, the transmitters need to tolerate

1872-408: 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

1924-561: The impedance to deviate from that of an ideal capacitor at higher frequencies. Transient load decoupling as described above is needed when there is a large load that gets switched quickly. The parasitic inductance in every (decoupling) capacitor may limit the suitable capacity and influence the appropriate type if switching occurs very fast. Logic circuits tend to do sudden switching (an ideal logic circuit would switch from low voltage to high voltage instantaneously, with no middle voltage ever observable). So logic circuit boards often have

1976-698: The intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=LVD&oldid=1003384540 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Low-voltage differential signaling LVDS was introduced in 1994, and has become popular in products such as LCD-TVs, in-car entertainment systems, industrial cameras and machine vision, notebook and tablet computers , and communications systems. The typical applications are high-speed video, graphics, video camera data transfers, and general purpose computer buses . Early on,

2028-478: The multiple serial data channels. The original LVDS standard only envisioned driving a digital signal from one transmitter to one receiver in a point-to-point topology. However, engineers using the first LVDS products soon wanted to drive multiple receivers with a single transmitter in a multipoint topology. As a result, NSC invented Bus LVDS (BLVDS) as the first variation of LVDS designed to drive multiple LVDS receivers. It uses termination resistors at each end of

2080-400: The notebook computer and LCD display vendors commonly used the term LVDS instead of FPD-Link when referring to their protocol, and the term LVDS has mistakenly become synonymous with Flat Panel Display Link in the video-display engineering vocabulary. LVDS is a differential signaling system, meaning that it transmits information as the difference between the voltages on a pair of wires;

2132-429: The opposite direction via the other wire. From Ohm's law , the voltage difference across the resistor is therefore about 350  mV . The receiver senses the polarity of this voltage to determine the logic level. As long as there is tight electric- and magnetic-field coupling between the two wires, LVDS reduces the generation of electromagnetic noise. This noise reduction is due to the equal and opposite current flow in

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2184-506: The possibility of other transmitters simultaneously driving the same bus. Point-to-point LVDS typically operates at 3.5 mA. Multi-point LVDS or bus LVDS (B-LVDS) can operate up to 12 mA. Bus LVDS and LVDM (Low-Voltage Differential Multipoint) (by TI ) are de facto multipoint LVDS standards. Multipoint LVDS ( MLVDS or M-LVDS ) is the TIA standard (TIA-899). The AdvancedTCA standard specified MLVDS for clock distribution across

2236-417: The power supply onto its output. In these applications, the decoupling capacitors are often called bypass capacitors to indicate that they provide an alternate path for high-frequency signals that would otherwise cause the normally steady supply voltage to change. Those components that require quick injections of current can bypass the power supply by receiving the current from the nearby capacitor. Hence,

2288-448: The serializer and deserializer, abbreviated to SerDes when the two devices are contained in one integrated circuit. As an example, FPD-Link actually uses LVDS in a combination of serialized and parallel communications. The original FPD-Link designed for 18-bit RGB video has 3 parallel data pairs and a clock pair, so this is a parallel communication scheme. However, each of the 3 pairs transfers 7 serialized bits during each clock cycle. So

2340-526: The signal transmitted as a differential signal helps for EMC reasons. However, high-quality shielded twisted-pair cables must be used together with elaborate connector systems for cabling. An alternative is the use of coaxial cables. Studies have shown that it is possible in spite of the simplified transfer medium dominate both emission and immunity in the high frequency range. Future high-speed video connections can be smaller, lighter, and cheaper to realize. Serial video transmission technologies are widely used in

2392-401: The slower power supply connection is used to charge these capacitors, and the capacitors actually provide large quantities of high-availability current. A transient load decoupling capacitor is placed as close as possible to the device requiring the decoupled signal. This minimizes the amount of line inductance and series resistance between the decoupling capacitor and the device. The longer

2444-576: 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 (SATA), RapidIO , and SpaceWire use LVDS to allow high speed data transfer. Intel and AMD published

2496-670: 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

2548-451: The switching event has finished, so that the load can draw full current at normal voltage from the power supply and the capacitor can recharge. The best way to reduce switching noise is to design a PCB as a giant capacitor by sandwiching the power and ground planes across a dielectric material. Sometimes parallel combinations of capacitors are used to improve response. This is because real capacitors have parasitic inductance, which causes

2600-416: The switching. In a subcircuit, switching will change the load current drawn from the source. Typical power supply lines show inherent inductance , which results in a slower response to changes in current. The supply voltage will drop across these parasitic inductances for as long as the switching event occurs. This transient voltage drop would be seen by other loads as well if the inductance between two loads

2652-414: The two wire voltages are compared at the receiver. In a typical implementation, the transmitter injects a constant current of 3.5  mA into the wires, with the direction of current determining the digital logic level. The current passes through a termination resistor of about 100 to 120 ohms (matched to the cable's characteristic impedance to reduce reflections) at the receiving end, and then returns in

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2704-399: The two wires creating equal and opposite electromagnetic fields that tend to cancel each other. In addition, the tightly coupled transmission wires will reduce susceptibility to electromagnetic noise interference because the noise will equally affect each wire and appear as a common-mode noise. The LVDS receiver is unaffected by common-mode noise because it senses the differential voltage, where

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