Inductors, Coils, and Chokes Specifications

Technology / Configuration



	Your choices are...
	Solenoidal (Standard) Core		Solenoidal cores or standard cores are rod-shaped.
	Toroidal		Toroidal inductors resemble doughnuts and differ in terms of diameter, thickness, permeability and type. They have a high inductance for the occupied physical space.
	Bobbin Core		Bobbin cores are shaped like a bobbin or spool. Inductors that use bobbin cores are available with or without leads and come in both axial and radial forms.
	Wirewound		Wirewound inductors have cores made of wound wires.
	Multilayer		Multilayer inductors are made by layering the coil between multiple layers of core material. Normally, the coil consists of a bare-metal material (no insulation). This technology is sometimes referred to as "non-wirewound". With multilayer inductors, the inductance value can be increased by adding additional layers to create a spiral pattern.
	Laminated		Laminated inductors or ferrite beads have a core that is made by stacking laminations on top of each other. Laminations are made from different materials and differ in terms of thickness.
	Other		Other unlisted, specialized, or proprietary types or technologies.
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Standards and Certifications


	RoHS Compliant		Restriction of Hazardous Substances (RoHS) is a European Union (EU) directive that requires all manufacturers of electronic and electrical equipment sold in Europe to demonstrate that their products contain only minimal levels of the following hazardous substances: lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyl and polybrominated diphenyl ether. RoHS will become effective on July 1, 2006.
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	WEEE Compliant		Waste Electrical and Electronics Equipment (WEEE) is a European Union (EU) directive designed to encourage the reuse, recycling and recovery of electrical and electronic equipment. WEEE seeks to improve the environmental impact and performance of such equipment, and establishes requirements and criteria for collection, treatment, recycling and recovery. In addition, WEEE makes producers responsible for financing such activities. For their part, retailers and distributors must provide a way for consumers to return used or obsolete equipment without charge.
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Core Material


	Core Material		Coils are wound on various materials and assembled into different shapes. The most popular materials are iron (e.g., iron alloys, laminations, or powder) and ferrite, a black, nonconductive, brittle magnetic material. Products are designed to multiply the inductance of a given coil by the "permeability" of the core material.
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	Air		The inductor does not have a material core.
	Ceramic		Ceramic cores provide a form for the coil. In some designs, they also create a structure to hold the terminals in place. Because ceramics lack magnetic properties, ceramic cores do not increase permeability. Ceramics also have a very low thermal coefficient of expansion, which allows for relatively high inductance-stability over a range of operating temperatures.
	Ferrite		Ferrite is a magnetic material that consists of a mixed oxide of iron and other elements with a crystalline molecular structure.
	Phenolic		Phenolic cores have a polyester base and good high-temperature characteristics. Products typically have a high flammability rating such as UL94V-0 and provide high strength. Phenolic cores are more economical than ceramic cores.
	Iron		The core material is iron.
	Powdered Iron		Powdered iron is a magnetic material with an inherent, distributed air gap that allows the core to store higher levels of magnetic flux, permitting a higher level of direct current (DC) to flow through the inductor before saturation occurs. Powdered iron cores are made of nearly 100% iron.
	Nickel - Iron		Cores are a combination of iron and nickel.
	MPP		Molypermalloy powder (MPP) is a magnetic material with an inherent, distributed air gap that allows the core to store higher levels of magnetic flux, permitting a higher level of direct current (DC) to flow through the inductor before saturation occurs. The basic materials of MPP are nickel (80%), molybdenum (2% to 3%), and iron (17% to 18%).
	Other		Other unlisted, specialized, or proprietary core materials.
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Performance


	Inductance Range		Inductance range is the range of inductance, the property of a circuit element to oppose any change in the flow-through of current. Inductance is influenced by an inductor's core material, shape and size. The turn count and shape of the coil are also important factors. The unit of inductance is the Henry (H).
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	Inductance Tolerance		Inductance tolerance is the allowed amount of variation from the nominal value as specified by the manufacturer.
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	DCR		Direct current resistance (DCR) is the resistance of the inductor winding as measured using DC current. DCR is usually minimized in the design of an inductor, and specified as a maximum rating.
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	Rated DC Current		The rated DC current (DC) is the level of continuous direct-current that can be passed through the inductor without damage. The DC-current level is based on a maximum temperature-rise at the maximum-rated ambient temperature. The rated current is related to the inductor's ability to minimize power losses in the winding by having a low DC resistance. For low-frequency currents, the RMS current can be substituted for the DC-rated current.
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	Quality Factor (Q)		An inductor’s quality factor or Q-value is a measure of the relative losses in the inductor. Q-value is defined as the ratio of inductive reactance to the effective resistance, or X_L/R_e. Since both X_L and R_e are functions of frequency, the test frequency must be given when specifying Q. At the self-resonant frequency (SRF), Q is zero because the inductance is zero.
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	SRF		Self resonant frequency (SRF) is the frequency at which an inductor's distributed capacitance resonates with its inductance. Because inductance equals capacitance, the values cancel each other out. An inductor at SRF acts as a purely resistive high-impedance element and has a Q-value of zero.
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	Operating Temperature		This is the full-required range of ambient operating temperature.
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	Impedance Range		Impedance is the total resistance to the flow of current, and includes both alternating current (AC) and direct current (DC). The DC component is the DC resistance of the device. The AC component includes the inductor reactance.
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	Impedance Tolerance		Impedance tolerance is the allowed amount of variation from the nominal value as specified by the manufacturer.
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	Testing Frequency		Testing frequency is the frequency at which inductors are tested for impedance, inductance, and/or quality factor.
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More Specs


	Lead Type
	Your choices are...
	Axial Leads		The inductor has a core with concentric leads on opposite sides. The leads exit the core's ends and run along its axis instead of coming out from the side.
	Radial Leads		The inductor has a core with leads that exit from the same side of the inductor body for mounting in the same plane.
	Flying Leads		Flying leads project horizontally.
	No Leads (SMT)		The inductor does not have leads, but instead uses surface mount technology (SMT).
	Tab Leads		Tab leads are terminals designed for direct mounting into a circuit-board socket.
	Gull-Wing Leads		Gull-wing leads are relatively inexpensive to mold and form. These popular leads are also flexible enough to withstand thermal expansion and contraction. Operators can easily inspect the integrity of a gull-wing lead in a circuit-board socket connection.
	J-Leads		J-leads use less circuit-board space than gull-wing leads; however, J-leads in board solder-connections are relatively difficult to inspect. J-leads are also more difficult to form.
	Other		Other unlisted, specialized or proprietary leads.
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	Packing Method
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	Tape Reel		Components are packed in tape reel assemblies that include a carrier tape with embossed cavities for storing individual components. A cover tape seals the carrier tape in place. This composite tape is then wound on a reel that is placed in a corrugated shipping box for transport and delivery. Customers unpack the reels and load them into industry-standard, pick-and-place board assembly equipment. Tape and reel assemblies provide component isolation and are designed for surface mount packages such as quad flat package (QFP) and thin quad flat package (TQFP). Typically, carrier tape is made from a polystyrene (PS) or PS-laminate film with a uniform film thickness between 0.2 mm to 0.4 mm. Carrier tape design is defined largely by component length, width, and thickness. Cover tape is made from a polyethylene teraphthalate (PET) film or film laminate with an adhesive applied to the underside of the film. This adhesive is usually heat and pressure sensitive to ensure a positive, consistent seal between the carrier tape and the cover tape. The reels that contain the composite tape are typically made of polystyrene and have one, two, or three parts. Reel dimensions meet EIA-481-1, EIA-481-2, and EIA-481-3 standards.
	Tray / Rail		Components are packed in trays (rails) that are made of carbon-powder or fiber materials and molded into rectangular outlines that contain matrices of uniformly spaced pockets. These containers protect components during shipping and provide proper component location and orientation for use with industry-standard, pick-and-place board assembly equipment. Trays are designed for components for that have leads on four sides and that require component lead isolation during shipping, handling, or processing. For example, quad flat package (QFP) and thin quad flat package (TQFP) components are often shipped in trays. To facilitate shipping and handling, trays are stacked and bound together in standard configurations. To provide rigidity, an empty cover tray is added to the top of the load. Typical stacking configurations consist of five full trays and one cover tray, and ten full trays and one cover tray. Customer requirements determine whether trays are shipped in single or multiple stacks.
	Shipping Tube / Stick Magazine		Components are packed in shipping tubes or stick magazines that are made of rigid polyvinylchloride (PVC) and extruded in industry-standard sizes. These containers protect components during shipping and provide proper component location and orientation for use with industry-standard, pick-and-place board assembly equipment. To facilitate shipping and handling, shipping tubes and stick magazines are usually loaded into intermediate containers such as boxes or bags to form standard quantities. Intermediate-level packing quantities for shipping tubes and stick magazines often vary by pin count and package type.
	Bulk Pack		Components are distributed as individual parts.
	Other		Other unlisted packing methods.
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	Molded Case		The inductor's case is formed with a moding process. Common molding processes include injection molding and transfer molding. Typically, molded inductors have well-defined body dimensions that consist of smooth surfaces and sharper corners than other case types.
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	Shielded		The core of a shielded inductor contains most of the magnetic field.
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