Effect of Magnetic Beads

Magnetic BeadsIt is designed to suppress high-frequency noise and Spike interference on signal lines and power cables, and also to absorb electrostatic pulses. Magnetic Beads are used to absorb ultra-high frequency signals, such as RF circuits, PLL, oscillating circuits, and ultra-high frequency memory circuits (ddrsdram, Rambus, etc.). They need to be added to the power input part, inductance is a type of energy storage component used in LC oscillator circuit, medium and low frequency filter circuit, and its application frequency range rarely exceeds 50 MHz. Magnetic Beads have high resistivity and magnetic permeability, which is equivalent to a series of resistance and inductance, but the resistance value and Inductance Value Change with frequency.

Functions of magnetic beads

The function of magnetic beads is mainly to eliminate RF noise in transmission line structures (circuits). RF energy is an AC Sine Wave component superimposed on the DC transmission level. DC composition is a useful signal, however, RF energy is useless for electromagnetic interference transmission along the line and radiation (EMI ). To eliminate unnecessary signal energy, use a chip magnetic bead to act as a high-frequency resistor (the attenuation). The device allows the DC signal to pass through and filter out the AC signal. Generally, the high-frequency signal is above 30 MHz. However, the low-frequency signal is also affected by the chip magnetic beads.

Magnetic Beads have high resistivity and magnetic permeability, which is equivalent to a series of resistance and inductance, but the resistance value and Inductance Value Change with frequency. It has better high-frequency filtering characteristics than ordinary inductor, and presents resistance at high frequencies, so it can maintain a high impedance within a very wide frequency range, thus improving the FM filtering effect.

Magnetic beads can be used as power filters and inductor can be used. The circuit symbol of the magnetic beads is inductance, but the model shows that the magnetic beads are used. In terms of circuit functions, the magnetic beads and inductor work in the same principle, but the frequency characteristics are different.

Magnetic Beads are composed of oxygen magnets, and the inductance is composed of a magnetic core and a coil. The magnetic beads convert the AC signal into heat energy, and the inductance stores the AC and slowly releases it out.

Magnetic Beads have a great obstacle to high-frequency signals. The general specification is 100 euro/100 MHz, and its resistance is much smaller than the inductance at low frequencies.

Ferrite Bead is a fast-growing anti-interference component. It is cheap and easy to use, and has a significant effect on filtering out high-frequency noise.

In a circuit, as long as the wire passes through it (I use the ordinary resistance, the wire has passed through and glued, there is also a form of surface mount, but rarely seen sold ). When the current in the wire passes through, ferrite has almost no impedance on the low-frequency current, but it will have a great attenuation effect on the high-frequency current. High-frequency current is emitted in the form of heat. Its Equivalent circuit is a series of inductance and a resistor. The values of the two components are proportional to the length of the magnetic beads. There are many types of magnetic beads. Manufacturers should provide technical indicators, especially the curve of the relationship between impedance and frequency of magnetic beads.

Some magnetic beads have multiple holes, and the component impedance (the square of the number of beads passed) can be increased when the wires pass through. However, the noise suppression capability increased at high frequencies cannot be as expected, however, it would be better to concatenate several magnetic beads.

Ferrite is a magnetic material that produces magnetic saturation due to excessive current, resulting in a sharp reduction in the magnetic conductivity. Large Current filtering should adopt specially designed magnetic beads, and pay attention to the heat dissipation measures.

Ferrite Magnetic Beads can be used not only in power supply circuit to filter out high-frequency noise (can be used for DC and AC output), but also widely used in other circuits, and their volume can be very small. Especially in digital circuits, pulse signals contain high-frequency harmonic waves, which are also the main source of high-frequency radiation. Therefore, magnetic beads can be used in such cases.

Ferrite Magnetic Beads are also widely used in Noise Filtering of signal cables.

Take the HH-1H3216-500 commonly used in power filter as an example, the meaning of each field of the model is:

HH is a series of it, mainly used for power filter, used for signal line is HB series;

1 indicates that a component encapsulates a magnetic bead. If it is 4, it encapsulates four beads side by side;

H indicates the composition of the substance. h, C, and m are used for intermediate frequency applications (50-200 MHz ),

T low frequency applications (50 MHz), s high frequency applications (200 MHz );

3216 encapsulation size, length 3.2mm, width 1.6mm, that is, 1206 encapsulation;

500 impedance (generally MHz), 50 ohm.

There are three main product parameters:

Impedance [Z] @ 100 MHz (OHM): Typical 50, minimum 37;

DC resistance (m ohm): maximum 20;

Rated current rated current (MA): 2500.