Differential signaling

differentialdifferential pairdifferential signalsdifferential inputdifferential signaldifferential signallinghigh voltage differentialdifferential drivedifferential driverdifferential ended signaling
Differential signaling is a method for electrically transmitting information using two complementary signals.wikipedia
121 Related Articles

Twisted pair

twisted-pairunshielded twisted pairshielded twisted pair
Differential pairs are usually found on printed circuit boards, in twisted-pair and ribbon cables, and in connectors.
This is known as differential signaling.

Single-ended signaling

single-endedsingle endedSignal Ground
The opposite technique is called single-ended signaling.
The main alternative to single-ended signaling is called differential signaling.

RS-422

EIA-422Macintosh serial portsRS-422 standard
The technique works for both analog signaling, as in balanced audio—and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express, DisplayPort, HDMI, and USB. Differential pairs generally carry differential or semi-differential signals, such as high-speed digital serial interfaces including LVDS differential ECL, PECL, LVPECL, Hypertransport, Ethernet over twisted pair, Serial Digital Interface, RS-422, RS-485, USB, Serial ATA, TMDS, FireWire, and HDMI etc. or else high quality and/or high frequency analog signals (e.g., video signals, balanced audio signals, etc.).
Differential signaling can transmit data at rates as high as 10 Mbit/s, or may be sent on cables as long as 1,500 meters.

RS-485

EIA-485RS485Serial
The technique works for both analog signaling, as in balanced audio—and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express, DisplayPort, HDMI, and USB. Differential pairs generally carry differential or semi-differential signals, such as high-speed digital serial interfaces including LVDS differential ECL, PECL, LVPECL, Hypertransport, Ethernet over twisted pair, Serial Digital Interface, RS-422, RS-485, USB, Serial ATA, TMDS, FireWire, and HDMI etc. or else high quality and/or high frequency analog signals (e.g., video signals, balanced audio signals, etc.).
RS-485 supports inexpensive local networks and multidrop communications links, using the same differential signaling over twisted pair as RS-422.

DisplayPort

DPeDPDisplay Port
The technique works for both analog signaling, as in balanced audio—and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express, DisplayPort, HDMI, and USB.
In a standard DisplayPort connection, each lane has a dedicated set of twisted-pair wires, and transmits data across it using differential signaling with ANSI 8b/10b encoding.

Low-voltage differential signaling

LVDSLVDlow voltage differential signaling
Differential pairs generally carry differential or semi-differential signals, such as high-speed digital serial interfaces including LVDS differential ECL, PECL, LVPECL, Hypertransport, Ethernet over twisted pair, Serial Digital Interface, RS-422, RS-485, USB, Serial ATA, TMDS, FireWire, and HDMI etc. or else high quality and/or high frequency analog signals (e.g., video signals, balanced audio signals, etc.).
Low-voltage differential signaling, or LVDS, also known as TIA/EIA-644, is a technical standard that specifies electrical characteristics of a differential, serial communications protocol.

Balanced audio

balancedunbalancedbalanced audio connector
The technique works for both analog signaling, as in balanced audio—and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express, DisplayPort, HDMI, and USB. Differential pairs generally carry differential or semi-differential signals, such as high-speed digital serial interfaces including LVDS differential ECL, PECL, LVPECL, Hypertransport, Ethernet over twisted pair, Serial Digital Interface, RS-422, RS-485, USB, Serial ATA, TMDS, FireWire, and HDMI etc. or else high quality and/or high frequency analog signals (e.g., video signals, balanced audio signals, etc.).
Signals are often transmitted over balanced connections using the differential mode, meaning the wires carry signals of opposite polarity to each other (for instance, in an XLR connector, pin 2 carries the signal with normal polarity, and pin 3 carries an inverted version of the same signal).

Balanced line

balancedbalanced pairbalanced circuit
This advantage is not directly due to differential signaling itself, but to the common practice of transmitting differential signals on balanced lines.
Lines carrying symmetric signals (those with equal but opposite voltages to ground on each leg) are often incorrectly referred to as "balanced", but this is actually differential signaling.

HDMI

Micro HDMIHDMI 1.4micro-HDMI
The technique works for both analog signaling, as in balanced audio—and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express, DisplayPort, HDMI, and USB. Differential pairs generally carry differential or semi-differential signals, such as high-speed digital serial interfaces including LVDS differential ECL, PECL, LVPECL, Hypertransport, Ethernet over twisted pair, Serial Digital Interface, RS-422, RS-485, USB, Serial ATA, TMDS, FireWire, and HDMI etc. or else high quality and/or high frequency analog signals (e.g., video signals, balanced audio signals, etc.).
If only ARC transmission is required, a single mode signal using the HEAC+ line can be used, otherwise, HEC is transmitted as a differential signal over the pair of lines, and ARC as a common mode component of the pair.

Electromagnetic interference

interferenceradio frequency interferenceradio interference
Since the receiving circuit only detects the difference between the wires, the technique resists electromagnetic noise compared to one conductor with an un-paired reference (ground).
Since the noise is common-mode, shielding has very little effect, even with differential pairs.

USB

USB 2.0micro-USBmicro USB
The technique works for both analog signaling, as in balanced audio—and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express, DisplayPort, HDMI, and USB. Differential pairs generally carry differential or semi-differential signals, such as high-speed digital serial interfaces including LVDS differential ECL, PECL, LVPECL, Hypertransport, Ethernet over twisted pair, Serial Digital Interface, RS-422, RS-485, USB, Serial ATA, TMDS, FireWire, and HDMI etc. or else high quality and/or high frequency analog signals (e.g., video signals, balanced audio signals, etc.).
USB signals are transmitted using differential signaling on a twisted-pair data cable with 90 Ω ± 15% characteristic impedance.

PCI Express

PCIePCIe 3.0PCI-E
The technique works for both analog signaling, as in balanced audio—and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express, DisplayPort, HDMI, and USB.
A lane is composed of two differential signaling pairs, with one pair for receiving data and the other for transmitting.

Serial ATA

SATAeSATAmSATA
Differential pairs generally carry differential or semi-differential signals, such as high-speed digital serial interfaces including LVDS differential ECL, PECL, LVPECL, Hypertransport, Ethernet over twisted pair, Serial Digital Interface, RS-422, RS-485, USB, Serial ATA, TMDS, FireWire, and HDMI etc. or else high quality and/or high frequency analog signals (e.g., video signals, balanced audio signals, etc.).
One such technique used in SATA links is differential signaling.

Current-mode logic

CMLcurrent mode logiccurrent mode
Current mode logic (CML)
Current mode logic (CML), or source-coupled logic (SCL), is a differential digital logic family intended to transmit data at speeds between 312.5 Mbit/s and 3.125 Gbit/s across standard printed circuit boards.

Microstrip

microstrip linemicrostrip linesmicrostrip transmission line
microstrip and stripline differential pair routing techniques on printed circuit boards
Most PCB design tools support such differential pairs.

SCSI

SASISmall Computer System InterfaceFast 20 UltraSCSI
SCSI equipment for example allows a maximum total cable length of 25 meters using HVD, while single-ended SCSI allows a maximum cable length of 1.5 to 6 meters, depending on bus speed.
Its standardization started as a single-ended 8-bit bus in 1986, transferring up to 5 MB/s, and evolved into a low-voltage differential 16-bit bus capable of up to 320 MB/s.

Signal integrity

signal qualityhigh-speed data linkshigh-speed digital
Signal integrity
Examples of mitigation techniques for these impairments are a redesign of the via geometry to ensure an impedance match, use of differential signaling, and preemphasis filtering, respectively.

Transition-minimized differential signaling

TMDSpanelLinktransition minimized differential signaling
Differential pairs generally carry differential or semi-differential signals, such as high-speed digital serial interfaces including LVDS differential ECL, PECL, LVPECL, Hypertransport, Ethernet over twisted pair, Serial Digital Interface, RS-422, RS-485, USB, Serial ATA, TMDS, FireWire, and HDMI etc. or else high quality and/or high frequency analog signals (e.g., video signals, balanced audio signals, etc.).
TMDS is similar to low-voltage differential signaling (LVDS) in that it uses differential signaling to reduce electromagnetic interference (EMI) which allows faster signal transfers with increased accuracy.

Differential TTL

Differential TTL
With a differential pair of wires, roughly the same unwanted voltage is induced in each wire.

Information

informativeinputinputs
Differential signaling is a method for electrically transmitting information using two complementary signals.

Signal

signalselectrical signalelectrical signals
Differential signaling is a method for electrically transmitting information using two complementary signals.

Ground (electricity)

groundgroundinggrounded
The receiving circuit responds to the electrical difference between the two signals, rather than the difference between a single wire and ground.

Printed circuit board

circuit boardPCBprinted circuit boards
Differential pairs are usually found on printed circuit boards, in twisted-pair and ribbon cables, and in connectors. microstrip and stripline differential pair routing techniques on printed circuit boards

Ribbon cable

flat cableflat cablesribbon cables
Differential pairs are usually found on printed circuit boards, in twisted-pair and ribbon cables, and in connectors.

Ethernet over twisted pair

10BASE-T10BaseT10/100/1000
The technique works for both analog signaling, as in balanced audio—and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express, DisplayPort, HDMI, and USB. Differential pairs generally carry differential or semi-differential signals, such as high-speed digital serial interfaces including LVDS differential ECL, PECL, LVPECL, Hypertransport, Ethernet over twisted pair, Serial Digital Interface, RS-422, RS-485, USB, Serial ATA, TMDS, FireWire, and HDMI etc. or else high quality and/or high frequency analog signals (e.g., video signals, balanced audio signals, etc.).