It is well known that an inductor is an energy storage component and a magnetic bead is a consumer device. Different roles mean that the application fields of the two are not the same. Inductors are mostly used in power supply filter circuits. Magnetic beads are mostly used in signal loops. Magnetic beads for EMC are mainly used to suppress electromagnetic radiation interference, while inductors used in this respect are focused on suppressing conducted interference.
It is worth noting that although the functions played differently on the circuit, both the beads and the inductor can be used to handle electromagnetic interference. Magnetic beads are used to absorb ultra-high frequency signals, such as some RF circuits, PLLs, oscillating circuits, and ultra-high-frequency memory circuits (DDR SDRAM, RAMBUS, etc.), which need to add magnetic beads to the input part of the power supply, and the inductance is a kind of storage. The energy component is used in the LC oscillating circuit, the low-frequency filter circuit, etc., and its application frequency range rarely exceeds 50 MHz. The ground connection is generally inductive, the power supply connection is also inductive, and the signal line is magnetic.
In the case of high frequency resonance, the inductance is not as good as the magnetic beads. Magnetic beads can also absorb high frequency interference, and in this case the inductance has lost its original role. To understand why the inductor fails, it is necessary to understand the two ways of EMI, namely: radiation and conduction, and different ways to adopt different suppression methods. The former uses magnetic beads and the latter uses inductance. For the IO part of the wrench, the purpose of EMC can be used to isolate the IO part from the ground of the wrench with an inductor. For example, the ground of the USB and the ground of the wrench are separated by a 10uH inductor. It can prevent plugging noise from disturbing the ground plane.
Magnetic beads are used where analog ground and digital ground are combined. How large is the magnetic bead between the digital ground and the analog ground? The size of the magnetic bead (which should be exactly the characteristic curve of the magnetic bead) depends on the frequency of the interference wave that you need to absorb the magnetic beads. Why is the unit and resistance of the magnetic bead? The same? Magnetic beads are high-frequency resistance, low DC resistance, high-frequency resistance, so it is easy to understand, such as 1000R@100Mhz means that the signal of 100M frequency has 1000 ohm resistance, because the magnetic beads The unit is nominally based on the impedance it produces at a certain frequency, and the unit of impedance is also ohms. A characteristic curve of frequency and impedance is usually attached to the data sheet of the magnetic bead. Generally, the standard is 100MHz. For example, 2012B601 means that the Impedance of the magnetic bead is 600 ohms at 100 MHz.
In many products, the two grounds of the switch are connected by capacitors. Why not use inductors? If magnetic beads are used or directly connected, accidental levels such as static electricity of the human body will easily enter the ground of the switch, so that the switch works abnormally. But if they are disconnected, when they are struck by lightning or other high voltages, the electric spark between the two places will cause a fire. Adding a capacitor avoids this situation.
The ground of the switch is to eliminate harmonics by the capacitance between the two grounds. Like a high-impedance transformer, he adds a path to eliminate harmonics! The ferrite material is a ferro-magnesium alloy or an iron-nickel alloy. This material has a high magnetic permeability and can be used to make the inductance between the coil windings. The capacitance generated in the case of high frequency and high resistance is the smallest. Ferrite materials are often used at high frequencies because their main inductance characteristics at low frequencies make the losses on the line small. At high frequencies, they mainly exhibit a reactance characteristic ratio and change with frequency. In practical applications, ferrite materials are used as high frequency attenuators for RF circuits. In fact, the ferrite is preferably equivalent to the parallel connection of the resistor and the inductor. The resistor at the low frequency is short-circuited by the inductor, and the impedance of the inductor at a high frequency becomes so high that the current passes through the resistor. Ferrite is a consumer device in which high-frequency energy is converted into thermal energy, which is determined by its electrical resistance characteristics.
The difference between structural and actual production
From the appearance structure, we can also see the difference between the two. We can separate the inductor and the magnetic beads by the number of coils. More than one coil is called an inductive coil, and a coil of less than one turn (a straight through magnetic ring) is called a magnetic bead. The purpose is determined by the amount of inductance required.
In some products, the magnetic filter is replaced by an inductor. In fact, this is feasible, the circuit symbol of the magnetic beads is the inductance, but the model can be seen to use the magnetic beads. In terms of circuit function, the magnetic beads and the inductor are identical in principle, but the frequency characteristics are different.
This article begins with an in-depth analysis of the principle, helps you analyze the similarities and differences between the inductor and the magnetic bead, and finally provides a method of resolution from the perspective of structure and practical application. I hope that novice readers can quickly distinguish between inductors and beads after reading this article.
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