The method of electrically transmitting Information using two complementary signals is called differential signaling.
This is the technique that is capable of sending similar electrical signals, in the form of differential pairs, in its conductors. Differential signaling is used widely in two types of communication schemes. They are LVDS and TTL.
LVDS vs TTL
The difference between LVDS and TTL is that LVDS refers to the manner of information transmission while TTL refers to compatible signaling. In LVDS, there are two wires with a difference in voltage while TTL uses ground system reference for presence or absence of voltage in binary form of 0 or 1.
LVDS consumes about 350mV of voltage. LVDS provides inherent resistance to interference and the devices can therefore use longer wires.
LVDS uses twisted copper pairs that create high electromagnetic field coupling. They can stabilize voltage spikes. Unlike TTL, three reference point of LVDS is not the ground.
While TTL uses the supply from the transistor of about 5 V and consumes more power comparatively.
TTL does not provide inherent resistance and hence cannot stabilize voltage spikes which can result in an error of binary results. Since the mode of transmission is parallel, it requires separate wires and increases the number of wires.
|Parameters of Comparison||LVDS||TTL|
|Distance of transmission||Higher distance of transmission||Lower distance of transmission|
|Mode of transmission||Serial mode||Parallel mode|
|Power consumption||Low power consumption||High power consumption|
|Reference point||No usage of the ground system for reference signal||Uses ground as the reference signal|
|Application||In high-speed backplane, transmissions like cabled, board or clock distribution and widely in parts of communication and infotainment devices||Serial storage architecture (SSA) devised by IBM|
What is LVDS?
LVDS stands for Low-Voltage Differential Signalling. It is a standard unit that is used to differentiate specific electrical characteristics like serial or differential signaling.
It is commonly misunderstood as a protocol. LVDS requires low-power and high speed to operate and consists of twisted copper cables. It is also used as a data link layer on the top of the OSI model.
LVDS was discovered in 1994 by the National Semiconductor but gained popularity in the 1990s.
It is mainly used as a standard for high-speed data transfer in infotainment systems like LCD-TVs, computers, tablets, video cameras, and other communication systems.
Earlier among the engineers, the term LVDS was mistaken as synonymous with Flat Panel Display Link (FPD-Link). The computer monitor resolutions before the invention of LVDS lacked faster rates for graphics and videos.
The first application of LVDS was in 1992 when Apple Computer collaborated with National Semiconductor and developed QuickRing. It was an auxiliary bus for high-speed video data.
Currently, LVDS is used to replace PECL (Positive Emitter-Coupled Logic) in interconnecting multiprocessing systems.
LVDS devices without signal conditioning can received equalization and transmission up to several meters (about 16-20 meters) and offer a speed of less than equal to 155.5 Mbps in a low-power general interface.
What is TTL?
TTL stands for Transistor-transistor logic. It is installed in electronic devices to be resistant to noise. TTL is usually single-ended. The reference of TTL is system ground.
The voltage level can go low as 0-0.8 volts and high as 2-5 volts. TTL follows a similar principle as that of LVDS but operates on different levels of voltage.
TTL is used in long-distance signaling. It is efficient in the removal of unwanted voltage induced and only the voltage from the driver’s side remains. The differential type of TTL can form a current loop in the pair of wires.
There is no current exchange that occurs between the receiver and the driver and the signal current needs to return to the ground connection.
The logic used in TTL is binary coding with the presence or absence of voltage. The reference is the ground system which determined the binary whether 1 or 0.
TTL faces voltage spike during data transmission so thus provides faulty binary values. TTL also does not use lower voltage levels.
TTL follows a parallel mode of transmission. Its mode of transmission requires a longer and greater number of wires. It cannot support a higher distance of transmission. TTL also does not provide methods of lowering voltage levels.
Main Differences Between LVDS and TTL
- The full form of LVDS is Low Voltage Differential Signalling while the full form of TTL is Transistor-transistor Logic.
- Devices that use LVDS have a longer and more number of wires while devices that use TTL have a shorter and less number of wires.
- LVDS uses lower voltage levels while TTL uses higher voltage levels.
- LVDS is created to be more resistant to interference while TTL is not resistant to interference.
- LVDS transmits information in serial mode and can congregate several signals into one while TTL transmits information in parallel mode.
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