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Do You Know What Magnetic Beads Do?

2022-08-05

Magnetic beads are specially designed to suppress high-frequency noise and spike interference on signal lines and power lines, and also have the ability to absorb electrostatic pulses. Magnetic beads are used to absorb UHF signals. For example, some RF circuits, PLL, oscillating circuits, and UHF memory circuits (DDR SDRAM, RAMBUS, etc.), magnetic beads need to be added to the input part of the power supply. Inductor is a kind of energy storage element, which is used in LC oscillating circuits, medium and low frequency filtering circuits, etc., and its application frequency range rarely exceeds 50MHZ.


The function of magnetic beads is mainly to eliminate the RF noise existing in the transmission line structure (circuit). RF energy is the AC sine wave component superimposed on the DC transmission level. The DC component is the useful signal needed, while the RF energy is the useless electromagnetic interference transmission and radiation (EMI) along the line. To eliminate this unwanted signal energy, chip magnetic beads act as high-frequency resistors (attenuators), which allow DC signals to pass through while filtering out AC signals. Usually the high frequency signal is above 30MHz, however, the low frequency signal will also be affected by the chip magnetic beads.


Magnetic beads have very high resistivity and permeability, which is equivalent to the resistance and inductance in series, but the resistance value and inductance value vary with frequency. It has better high-frequency filtering characteristics than ordinary inductors, showing resistance at high frequencies, so it can maintain a higher impedance in a fairly wide frequency range, thus improving the frequency modulation filtering effect.


As a power filter, inductors can be used. The symbol of the magnetic bead circuit is the inductor, but the model shows that the magnetic bead is used. In terms of circuit function, the magnetic bead and the inductor have the same principle, only the frequency characteristics are different.


Magnetic beads are made up of oxygen magnets, and inductors are made up of a core and a coil. Magnetic beads convert AC signals into heat, and inductors store the AC and release it slowly.


Magnetic beads to high frequency signals have a greater obstacle, the general specification of 100 euros /100 MMHZ, it at low frequency resistance is much smaller than the inductor.


Ferrite bead is a kind of anti-interference component with rapid application development at present, which is cheap, easy to use, and has remarkable effect in filtering high-frequency noise.


in the circuit as long as the wires go through it (i use all of them like ordinary resistors, the wires have been crossed and glued, there are also surface mount forms, but they are rarely sold). When the current in the wire passes through, the ferrite has little resistance to the low frequency current, while the higher frequency current will have a large attenuation effect. The equivalent circuit is an inductor and a resistor in series, and the values of both components are proportional to the length of the magnetic bead. There are many kinds of magnetic beads. The manufacturer should provide technical specifications, especially the curve of impedance and frequency of magnetic beads.


Some magnetic beads have more than one hole, through the wire can increase the component impedance (through the square of the number of magnetic beads), but at high frequency increased noise suppression ability is not possible as expected, and the method of using more than a few magnetic beads in series will be better.


Ferrite is a magnetic material, due to excessive current through the magnetic saturation, the magnetic conductivity drops sharply. Magnetic beads specially designed in structure should be used for high current filtering, and attention should be paid to its heat dissipation measures.


Not only can it be used to filter high-frequency noise in power supply circuit (can be used for DC and AC output), but also can be widely used in other circuits, its volume can be made very small. Especially in the digital circuit, because the pulse signal contains high frequency harmonic, which is also the main source of high frequency radiation of the circuit, it can play the role of magnetic beads on this occasion.


The Type And Size Of The R6H Series Of Chart
1. R6H pattern and dimensions of five rings( SHAPE AND SIZE)  ( Unit: mm )
1.1 Six holes magnetic beads:  R6H-1.5T
Six holes magnetic beads:  R6H-2.5T
    
1.2

Six holes magnetic beads: R6H-2T

Six holes magnetic beads:  R6H-3T

    
1.3 Six holes magnetic beads: R6H-1.5T+1.5T
 
1.4 Six hole magnetic beaded tape: R6H-1.5T-T
 
1.5 Six hole magnetic bead U shape: R6H-1.5T-U
 

The five rings number

FREQ(MHZ)

Z min(Ω)

A

B

D

E

R6H-1.5T

100

180

15.0mm max

20.0mm

6.0±0.5mm

0.5±0.5mm

R6H-2T

100

400

15.0mm max

20.0mm

6.0±0.5mm

0.5±0.5mm

R6H-2.5T

100

600

15.0mm max

20.0mm

6.0±0.5mm

0.5±0.5mm

R6H-3T

100

680

15.0mm max

20.0mm

6.0±0.5mm

0.5±0.5mm

R6H-1.5T+1.5T

100

600

15.0mm max

20.0mm

6.0±0.5mm

0.5±0.5mm