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backplane in electronics printed circuit board


A backplane (or “backplane system”) is a circuit board (usually a printed circuit board) that connects several connectors in parallel to each other, so that each pin of each connector is linked to the same relative pin of all the other connectors[1], forming a computer bus. It is used as a backbone to connect several printed circuit board cards together to make up a complete computer system. One popular early computer system that used this approach was called the S-100 bus because the connectors used had one hundred pins. Early personal computers like the Apple II and the IBM PC integrated an internal backplane for expansion cards.

While a motherboard may include a backplane, the backplane is actually a separate entity. A backplane is generally differentiated from a motherboard by the lack of on-board processing power where the CPU is on a plug-in card.

Backplanes are normally used in preference to cables because of their greater reliability. In a cabled system, the cables need to be flexed every time that a card is added to or removed from the system; and this flexing eventually causes mechanical failures. A backplane does not suffer from this problem, so its service life is limited only by the longevity of its connectors. For example, the DIN 41612 connectors used in the VMEbus system can withstand 50 to 500 insertions and removals (called mating cycles), depending on their quality.

A backplane provides minimal functionality without a controlling Single Board Computer installed providing the CPU and other computer functions. A Single Board Computer meeting the PICMG 1.3 specification and compatible with a PICMG 1.3 backplane is referred to as a System Host Board.

A backplane can be used without an associated Single Board Computer to simply provide power to the plug-in cards. This is a common usage for companies manufacturing plug-in cards to power them for burn-in.

In addition, there are bus expansion cables which will extend a computer bus to an external backplane, usually located in an enclosure, to provide more or different slots than what the host computer provides. These cable sets have a transmitter board located in the computer, an expansion board in the remote backplane, and a cable between the two. Bus expansion cables do not need a Single Board Computer in the remote bus to control the I/O cards as that is provided by the expansion electronics.

Area of a computer or other device where various logic and control elements are interconnected. Often a printed circuit board into which other circuit boards plug at right angles. It’s high-speed communications line to which individual components are connected. In multi-plane fabric switches, the backplane allows for inter-fabric connections and timing distribution without the need for physical cables.

the term backplane refers to the large circuit board that contains sockets for expansion cards.

Backplanes are often described as being either active or passive. Active backplanes contain, in addition to the sockets, logical circuitry that performs computing functions. In contrast, passive backplanes contain almost no computing circuitry.

Traditionally, most PCs have used active backplanes. Indeed, the terms motherboard and backplane have been synonymous. Recently, though, there has been a move toward passive backplanes, with the active components such as the CPU inserted on an additional card. Passive backplanes make it easier to repair faulty components and to upgrade to new components.

A backplane is an electronic circuit board containing circuitry and sockets into which additional electronic devices on other circuit boards or cards can be plugged; in a computer, generally synonymous with or part of the motherboard.





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