Beads

Magnetic beads dedicated to inhibit signal, the power cord high-frequency noise and rush interference, but also has the ability to absorb electrostatic pulse. Magnetic beads are used to absorb uhf signals, like some RF circuit,, oscillating circuit, including PLL circuit (DDRSDRAM, uhf memory RAMBUS, etc.) are needed in the power input parts put magnetic beads, and inductance is a kind of energy storage devices, used in LC oscillating circuit, medium frequencies filter circuits etc, its application in frequency range rarely more than 50MHZ. Magnetic beads has high resistivity and magnetic conductance, equivalent to resistance and the inductance series, but resistance and inductance value on frequency changes.

Magnetic beads of the main function is to eliminate exists in transmission line structure (the RF circuit), RF energy noise is superimposed on dc transmission level exchanges sinusoidal components, dc component is need useful signal, but RF RF energy is useless along lines of electromagnetic interference (EMI) transmission and radiation. To eliminate these don't need signal energy, using chip magnetic beads play the role of high-frequency resistance (attenuator), this device allows dc signal through, to filter out the ac signal. Usually the high frequency signal for 30MHz above, however, the low frequency signal is also under the influence of chip magnetic beads.

Magnetic beads has high resistivity and magnetic conductance, he equivalent to resistance and the inductance series, but resistance and inductance value on frequency changes. He than ordinary inductance have better high-frequency filtering properties in high frequency appears when resistance sex, so can in a quite wide frequency range at high impedance, so as to improve the frequency modulation effect of filter.

As power filtering, can use inductor. Magnetic beads circuit symbol is inductance but model can be seen above is using magnetic beads in circuit function, magnetic beads and inductance is the same principle, just frequency characteristic differ.

Magnetic beads composed by oxygen magnets, inductance coil and composed by cores, magnetic beads the ac signal is transformed into heat energy, inductance to exchange stored slow release out.

Magnetic beads of the high frequency signal to have larger side effect, the general specification has 100 European / 100mMHZ, it in low frequency resistance than inductance much smaller. Ferrite beads are currently used a anti-jamming is developing very fast, cheap, easy to use, component filter high-frequency noise effect significantly.

In a circuit as long as wires through it can (I am using is like ordinary resistance wire shape of, already through and agglutination, also have SMT forms, but seldom see sell). When the conductor in electric current passes ferrite in low-frequency current almost no impedance, but to the current higher frequencies produces more attenuation function. Hf-current in which heat form to send out, the equivalent circuit for an inductor and a resistor in series, two components of value and the length of the magnetic beads in proportion. Magnetic beads manufacturer shall provide a lot of more phyletic, technical indexes explain, especially magnetic beads of impedance and frequency relations of the curve.

Some magnetic beads on multiple hole, with wires through can increase the component impedance (through magnetic beads times of square), but in the high frequency increases when the noise restraining ability impossible as expected, and with several magnetic beads series of measures will be better off.

Ferrite magnetic material, because the meeting is caused by excessive current magnetic saturation, the permeability sharply. Large current filter should adopt structure on the special design of magnetic beads, but also pay attention to the heat dissipation measures.

Ferrite beads can be used not only in the power circuit filtering out the high-frequency noise (can be used in the dc and ac output), also can be widely applied to the other circuit, the volume can do to be small. Especially in digital circuits, due to the high frequency pulse signal contain higher harmonic radiation, but also the primary sources of high-frequency circuits on this occasion, so can play the role of magnetic beads.

Ferrite beads also widely used in signal cable noise filter.

To often used in power filtering the HH 1H3216-500 - for example, its type each field meaning is as follows:

HH is its a series, mainly used for power filtering, used for signal is HB series,

1 if a module seal a magnetic beads, if for four is four abreast encapsulation,

H. says the composition of the substance, H, C, M for intermediate frequency application (50-200MHz),

T low-frequency applications (50MHz), high frequency application (S); 200MHz

3216 encapsulation size, long 320 mm, wide 1.6 mm, namely 1206 encapsulation,

500 impedance (usually 100MHz), 50 ohm.

Its products mainly have three parameters:

Impedance [Z] @ 100MHz (50 ohm) : 37; Minimum living,

DC Resistance DC ohm Resistance (m) : can 20;

Rated Current is Rated (mA) : 25.

The principle

Magnetic beads the major raw materials for ferrite. Ferrite is a kind of cubic lattice structure of ferrous magnetic materials. Ferrite materials for magnesium alloy or iron and nickel alloy iron, its manufacturing process and the mechanical properties and the ceramic similar, color is black. Emi filter is frequently used is a kind of magnetic ferrite materials, many vendors provide specially for the electromagnetic interference suppression of ferrite materials. This material is characteristic of loss at high frequency is very large, has the very high permeability, he can be inductor winding between the high-frequency high resistance produce capacitance minimum. To restrain electromagnetic interference with the ferrite, the most important performance parameters for magnetic conductance mu and saturation magnetic flux density Bs. Magnetic conductance muon can be expressed as a plural, real part inductance, XuShu segments representing the loss, as frequency increases. Therefore, its equivalent circuit for inductance L and resistance R composed of a series circuit, L and R is frequency of functions. When the conductor through the ferrite magnetic cores, which constituted inductance impedance in form is as frequency increases, but in different frequency its mechanism is completely different.

At low frequencies, the impedance by the inductance of the inductance components, low frequency magnetic core of small, R magnetic permeability is taller, accordingly inductance large quantities, L plays the leading role, electromagnetic interference is reflected suppressed, and then magnetic loss is lesser, the whole device is a low loss, high Q characteristics of the inductance, this inductance easy to cause the resonant therefore at low frequency and sometimes may appear use ferrite beads after interference enhance phenomenon.

At high frequencies, impedance by resistance components, with frequency increases, magnetic core magnetic conductivity is reduced, cause the inductance of the inductance quantity decreases, and inductance components, then decreased but magnetic loss increases, resistance components increase, so the overall impedance increases, when the high frequency signal through ferrite, electromagnetic interference is absorbed and translated into heat energy dissipation of form off.

Ferrite inhibit components are widely used in printed circuit board, lines and data lines. As in the PCB's power supply cord entry plus ferrite inhibit components, can filter out the high frequency interference. Ferrite magnetic beads or they can do little to curb signal, special power of high frequency interference and rush interference, it also has the absorption of electrostatic discharge pulse jamming ability.

Two components of numerical size and length of magnetic beads, and magnetic beads is proportional to the length of the inhibitory effect have obvious influence on the longer length, magnetic beads inhibit the better the results.

As power filtering, can use inductor. Magnetic beads circuit symbol is inductance but model can be seen above is using magnetic beads in circuit function, magnetic beads and inductance is the same principle, just differ magnetic beads frequency characteristics by oxygen magnets composition, inductance coil and composed by cores, magnetic beads the ac signal is transformed into heat energy, inductance to exchange stored slow release out. Magnetic beads of the high frequency signal to have larger side effect, the general specification has 100 European / 100mMHZ, it in low frequency resistance than inductance much smaller. FerriteBead is currently used to develop quickly a anti-interference components, cheap, easy to use, filter high-frequency noise effect significantly.