In this tutorial we are going to learn what is Use of Ferrite Beads in Design?
In Design for Bypassing between the +V and ground is critical because the object is for the capacitance to supply the current used in the device for switching. If the current is not available in the bypassing loop, because of too much inductance, the laws of physics say that the current should come to the lowest impedance, which then is from the leads connecting to the power supply. The power routing of distributed capacitance becomes the source for the higher frequencies. Because, the ferrite bead blocks the sourcing of RF current from the power line connection, forcing the microcomputer to live off the current available inside the ferrite bead It is of the utmost importance to realize, and always keep in mind, that the power-routing purpose is only to replenish the charge in the bypassing capacitor, and that the bypassing capacitor should supply all currents at either above the oscillator frequency. Keeping RF off the power distribution traces is accomplished using these measures can see in image.
- When Use a ferrite bead and a bypassing capacitor (0.1 F or 0.01 F), then placing the capacitors inside the ferrite bead and also Place a 1000-pF capacitor outside the ferrite bead, creating a PI filter. There should be Use the micro ground for the ground connection of this capacitor. If there is a lot of noise on this point, then the capacitor could couple that noise back onto the +V line.
- Always use the ferrite bead on +V trace, not on ground trace, when a through-hole ferrite bead is used, then it should be mounted with the exposed lead connected to +V.
- If apply the 3:1 length-to-width rule for traces in the bypassing loop, which is use to minimize impedance in this high-frequency path.
- Create the bypassing loops as small as possible in area and length. If tying the bypass capacitors for the oscillator or +V supply, try to extend the main ground rather than running a trace. Make a run any trace back over any other segment of the loop to reduce the radiating area when viewed from the top of the board.
- This types of ferrite beads is It is acceptable and beneficial to use ferrite beads and the same bypassing values on four-layer boards. The 1000-pF capacitor may not be needed on four-layer boards, but it should be drawn in the initial design, and deleted later if screen-room testing shows that it is not needed.