Inductance, magnetic beads, and 0 euro Resistance

InductanceIt is an energy storage component. It is mostly used in power supply filtering circuit, LC oscillating circuit, medium and low frequency filtering circuit, and its application frequency rarely exceeds 50 MHz. The inductance is directly proportional to the frequency. This can be illustrated by the formula XL = 2 π FL, in which XL is inductive resistance (in the unit of Ω ). For example, an ideal 10 MH inductor with a sensitivity of 628 Ω at 10 kHz and increased to 100 Mbit/s at MHz. Therefore, at 100 MHz, this inductance can be considered as an open circuit ). At MHz, if a signal passes through the inductance, the quality of the signal will decrease.

 

SPU square SMD Inductor

 

Magnetic rod Inductance

Magnetic ring Inductance

Core Inductance

Enclosed Inductor

Filter throttling

Color Ring Inductance

 

Ferrite Bead)The materials are magnesium iron or iron-nickel alloys, which have a high resistivity and magnetic permeability, at a high frequency and high impedance, the capacitance value between the coil within the inductor will be minimal. Magnetic Beads are generally only applicable to high-frequency circuits, because at low frequencies, they basically maintain the complete characteristics of inductance (including resistance and resistance components), which may cause slight loss on the line. At high frequencies, it basically only has the resistance component (J ω L), and the resistance component will increase as the frequency increases. For example, some RF circuits, PLL, oscillating circuits, including ultra-high frequency memory circuits (DDR, SDRAM, Rambus, etc.) All need to be added to the power input part with magnetic beads. In fact, magnetic beads are a high-frequency attenuation of RF energy. In fact, the magnetic beads can be considered as a resistor in parallel and an inductor. At low frequencies, the resistance is "short-circuited" by the inductance, current, and flow to the inductor. at high frequencies, the high inductance resistance forces the current flow resistance. Essentially, a magnetic bead is a dissipative device that converts high-frequency energy into heat. Therefore, in terms of performance, it can only be interpreted as a resistor, rather than an inductor.

 

 

 

The zero-euro resistance has the following functions:

A resistance with a resistance value of 0 ohm is called a 0 euro resistance.

First of all, we should understand that 0 euro resistance is only available in ideal conditions. In reality, it does not exist. Only the resistance of 0 euro is as close as possible.

0 euro resistance has the following functions:

1. There is no function in the circuit, just for convenience of debugging or Compatibility Design on the PCB.

 

2. patch cords can be used for both aesthetic and convenient installation. If a line does not need to be added, do not paste the resistor directly (does not affect the appearance ).

 

3. When the parameters of the matching circuit are uncertain, the parameter is replaced by 0 ohm. during actual debugging, the parameter is determined and replaced by the component of a specific value.

 

4. When you want to test the current consumption of some circuits, you can remove the 0ohm resistor and connect it to the current meter to facilitate the current consumption test.

 

5. When wiring, you can add a 0-euro resistor if it cannot be deprecated.

 

6. Act as an inductor or capacitor under a high-frequency signal. Inductance is used to solve EMC problems. Such as location, power supply, and IC pin.

 

7. Single Point Grounding (Protection grounding, working grounding, DC grounding are separated from each other on the equipment, and each of them becomes an independent system .)

 

8. Use fuses. Because the circuit breaking current on the PCB is large, if short-circuit and overcurrent faults occur, the circuit breaking may lead to more serious accidents. Because 0-euro resistance and current capacity are relatively weak (in fact, 0-euro resistance also has a certain degree of resistance, but it is only small), the 0-euro resistance will be broken first when the flow is over, thus, the circuit is disconnected to prevent larger accidents. Sometimes the fuse is made with a small resistor with a resistance of a few or a few euros. However, this is not recommended for use, but some vendors will use it to save costs.

 

9. Single Point Grounding in analog and digital locations. As long as the ground is connected together, the ground is connected to the Earth. If it is not connected together, it is "floating", there is a pressure difference, it is easy to accumulate the charge, resulting in static electricity. The ground refers to the 0 potential, and all voltages are obtained from the reference ground. The ground standards must be consistent, so all kinds of ground should be transient together. People think that the earth can absorb all the charge and always maintain stability, which is the final reference point. Although some boards are not connected to the earth, power plants are connected to the earth, and the power supply on the boards will eventually return to the power plant. If the simulated area is directly connected to the digital area, mutual interference will occur. There are four ways to solve this problem:

1. Use a magnetic bead to connect the device;

2. Connect with a capacitor;

3. Connect with an inductor;

4. Connect with a 0 ohm resistor.

 

The equivalent circuit of a magnetic bead is equivalent to a band-resistance wave limiting device, which only significantly blocks noise at a certain frequency point. It is necessary to estimate the noise frequency in advance so as to select an appropriate model. Magnetic beads do not match when the frequency is uncertain or unpredictable.

The capacitor is separated directly, causing float.

The inductance is large in size and has many stray parameters, which is unstable.

0 euro resistance is equivalent to a very narrow current path, which can effectively limit the Loop Current and suppress noise. Resistance degrades in all frequencies (0 euro resistance also has impedance), which is stronger than magnetic beads.

 

10. Used for current circuit during cross-connection * When the electrical ground plane is split, the shortest reflux path of the signal is broken. At this time, the signal loop has to bypass to form a large loop area, the influence of the electric field and the magnetic field becomes stronger, and it is easy to interfere with/be disturbed. The split zone is connected with 0 euro resistance, which can provide a shorter reflux path to reduce interference. * Configuration circuit * generally, no jumper or dial switch is allowed on the product. Sometimes users may tamper with the settings, which may cause misunderstanding. In order to reduce maintenance costs, use 0 euro resistance instead of jumper and other welding on the board. A vacant jumper is equivalent to an antenna at a high frequency. It works well with SMD resistors.

 

11. for other purposes, cross-line debugging/testing during cabling, and temporary replacement of other SMD devices as temperature compensator are more often due to EMC countermeasure needs.

 

12. Used as the configuration circuit. This function is similar to patch cord or dial switch, but it is fixed by welding, so that common users can modify the configuration at will. By installing resistance at different positions, you can change the function or set the address of the circuit.

 

In addition, the 0 ohm resistance is smaller than the parasitic inductance of the passing hole, and the passing hole will also affect the ground plane (because the hole needs to be dug)

Inductance, magnetic beads, and 0 euro Resistance