Inductance, allowable deviation and distributed capacitance of SMD inductor

Chip inductors, also known as power inductors, high current inductors and surface-mounted high power inductors.Features: miniaturization, high quality, high energy storage and low resistance.

The power SMT inductor is divided into two types: magnetic housing and without housing, mainly composed of magnetic core and copper wire.It mainly plays a filtering and oscillating role in the circuit.

The main parameters of SMD inductor include inductance, allowable deviation, distributed capacitance, rated current and quality factor.

1. Inductance: no-load measurement (theoretical value) and measurement in actual circuit (actual value).Because the inductor USES too many actual circuits, it is difficult to class.Measurements are explained only in the case of no load.

The size of the inductance, mainly depends on the number of winding (turns) of the inductance coil, winding mode, whether there is a magnetic core and the core of the material.In general, the more coils, the denser the coil, the greater the inductance.A coil with a core has a greater inductance than a coil without a core.The higher the core permeability, the greater the inductance.So the inductance is determined by a number of factors.The basic unit of inductance is the Henry, denoted by the letter "H".Other common units are milliheng (mH) and microheng (H).Mh 1 = 1000 mu H

2. Allowable deviation: an English letter is used to represent the allowable deviation after the unit of inductance, and the allowable deviation represented by each letter is shown in the table below.For example, 560uHK means the nominal inductance is 560uH, the allowable deviation is 10%, and the text symbol is the French text symbol method, which is to combine the nominal value and allowable deviation value of the inductor on the inductor body according to a fixed law of Numbers and text symbols.This notation is usually used in small power inductors whose units are usually nH or pH, with N or R for the decimal point.For example, 4N7 means inductance is 4.7nh, 4R7 means inductance is 4.7uh;47N means inductance of 47nH, and 6R8 means inductance of 6.8uh.

The allowable error value between the labeled sense and the actual sense.Generally used in oscillation or filter circuit, SMT inductance requires high precision, the allowable deviation is ±0.2%~±0.5%.The accuracy for coupling or high frequency choke is not high, the allowable deviation is ±10%~15%.

3. Distributed capacitance: the capacitance between the turns of the coil and between the coil and the magnetic core.The smaller the distributed capacitance, the better its stability.

Usually the analog circuit area and the digital circuit area are reasonably separated, the power line and the ground line are drawn out separately, and the power supply point is collected to a point.And if in the family integrated wiring, to meet 220V power supply lines telephone lines, network lines and audio, video lines, such as separate wiring, and as far as possible not to lay parallel.