Also circuits built via the antifuse's permanent conductive paths may be faster than similar circuits implemented in PLDs using SRAM technology. They may be less susceptible to alpha particles which can cause circuits to malfunction. Antifuse PLDs have advantages over SRAM based PLDs in that like ASICs, they do not need to be configured each time power is applied. Antifuse PLDs are one time programmable in contrast to other PLDs that are SRAM-based and which may be reprogrammed to fix logic bugs or add new functions. In this respect, these street light loops operated identically to the above mentioned Christmas light strings.Īntifuses in integrated circuits Īntifuses are widely used to permanently program integrated circuits (ICs).Ĭertain programmable logic devices (PLDs), such as structured ASICs, use fuse technology to configure logic circuits and create a customized design from a standard IC design. These contacts had a dual purpose - they connected the socket to the mounting assembly inside the luminaire, and the upper portion of these contacts held a replaceable, dime-size 'cutout' (an early form of antifuse). Each luminaire had a removable light socket, which had a pair of contacts that extended above the socket. Often a special bulb with no antifuse and often a slightly different rating (so it blows first as the voltage gets too high) known as a "fuse bulb" is incorporated into the string of lights to protect against the possibility of severe overcurrent if too many bulbs fail.Ī much earlier application of antifuses was in the old series-connected streetlights. Occasionally, the insulation fails to break down on its own, but tapping the blown lamp will usually cause it to make a connection. The insulation of the antifuse wire withstands the ordinary low voltage imposed across a functioning lamp but rapidly breaks down under the full mains voltage, giving the antifuse action. The antifuse is made using wire with a high resistance coating and this wire is coiled over the two vertical filament support wires inside the bulb. This rapidly causes the antifuse to short out the blown bulb, allowing the series circuit to resume functioning, albeit with a larger proportion of the mains voltage now applied to each of the remaining lamps. When the bulb blows, the entire mains voltage is applied across the single blown lamp. (The larger, traditional, C7 and C9 style lights are wired in parallel and are rated to operate directly at mains voltage.) Because the series string would be rendered inoperable by a single lamp failing, each bulb has an antifuse installed within it. Ordinarily (for operation from mains voltages), the lamps are wired in series. This technology has many applications.Īntifuses are best known for their use in mini-light (or miniature) style low-voltage Christmas tree lights. Whereas a fuse starts with a low resistance and is designed to permanently break an electrically conductive path (typically when the current through the path exceeds a specified limit), an antifuse starts with a high resistance, and programming it converts it into a permanent electrically conductive path (typically when the voltage across the antifuse exceeds a certain level). JSTOR ( May 2014) ( Learn how and when to remove this template message)Īn antifuse is an electrical device that performs the opposite function to a fuse.Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.
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