Use of magnetic beads

1. Magnetic Beads are mainly used for EMI noise suppression (for power supply or signal line). Their DC impedance (DCR) is very small but has a high impedance at high frequencies. 2. When selecting a magnetic bead, in addition to selecting an appropriate package, focus on it:
1) rated current (MA)
2) DC impedance (DCR) DC resistance (m ohm)
3) impedance [Z] @ 100 MHz (OHM)/magnetic bead impedance at noise center frequency (OHM) 3. magnetic Bead impedance generally refers to the impedance at 600 MHz. For example, a r magnetic bead indicates that the impedance at MHz is Euro. 4. The selection of magnetic beads parameters should be based on the actual situation. Example:
Hypothesis
1) Input Power Grid table on the left side of the magnetic beads: 3.2vdc + 300 mvpp @ 100 MHz (the second half is the power center frequency noise)
2) requirements on the right side of the magnetic beads: VDC> = 3.0vdc
Vn <= 50 mvpp @ 100 MHz
AC load> = 50 euro @ 100 MHz
DC current <= 300mA
So
1) Calculate the DC resistance of magnetic beads DCR:

DCR <= (3.2vdc-3.1vdc)/300mA = 0.3 Euro 2) calculate noise suppression magnetic beads impedance @ 100 MHz> = (300mvpp-50mvpp) /50mvpp * 50 euro = 250 euro magnetic beads should be selected at will:
 
(1) DCR <= 0.3 Euro
(2) 250 MHz impedance> = EURO
(3) The rated current is greater than or equal to 300 mA. If you select a magnetic bead with an impedance of 50 euro, the suppression effect is only half. In other words, the output on the right side of the magnetic bead may produce mvpp noise. In addition, from the technical point of view, the above (1) and (2) are in conflict. Therefore, before selecting a magnetic bead, you must first make a preliminary estimation of the noise (noise center frequency, amplitude, and suppression size) and DC of the circuit. Then select the appropriate parameter. 5. The parameter description in the bead name indicates that the beads are generally the same as the resistors and are represented by scientific and technical means. For example, 601 indicates the beads of 600 euro @ MHz.

For example, the commonly used power filter HH-1H3216-500:
-Hh is a series of it, mainly used for power filter, and 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), 50x10 ^ 0 = 50 ohm. When you buy magnetic beads, they do not necessarily understand DCR, impedance. Because the customers who buy at the same time seldom pay attention to magnetic beads.
Impedance parameters or something, and the people who do not sell them almost do not understand these parameters. However, at the scene, you can obtain the nominal size of the magnetic beads.
Model (such as HH-1H3216-500), at least the last represents the impedance can still be seen. If the people at the site do not know
DCR or non-MHz impedance parameters, you can get the model and Google or Baidu.