Interference suppression components for microcontroller systems

　　1. Decoupling capacitors

　　A decoupling capacitor should be configured between the power supply and ground of each integrated circuit, which can filter out the high-frequency noise from the power supply. As an energy storage element, it absorbs or provides the current change (di/dt) caused by the conduction and cutoff of the internal transistor of the integrated circuit, thereby reducing the system noise. Monolithic capacitors or ceramic capacitors with good high-frequency characteristics should be selected as decoupling capacitors. A large-capacity energy storage capacitor should be placed at the place where the power supply of each printed circuit board is introduced. Due to the winding structure of the electrolytic capacitor, its distributed inductance is large and it has almost no effect on filtering high-frequency interference signals. It should be used in pairs with decoupling capacitors. Tantalum capacitors are more effective than electrolytic capacitors.

　　2. Inductance that suppresses high frequencies

　　A high-frequency choke device is formed by inserting a thick enameled wire into a ferrite core with several holes in the axial direction. Inserting it in series with the power line or ground line can prevent high-frequency signals from being introduced from the power/ground line. This component is particularly suitable for separating the power supply of the analog circuit area, digital circuit area, and high-power drive area on a printed circuit board. It should be noted that it must be placed between the energy storage capacitor and the power supply in this area and cannot be placed between the energy storage capacitor and the electrical device.

　　3. Resettable fuse

　　This device is made of a new type of polymer material. When the current is lower than its rated value, its DC resistance is only a few tenths of an ohm. When the current reaches a certain level, its resistance rises rapidly, causing heat, and the higher the heat, the greater the resistance, thus blocking the power supply current. When the temperature drops, it can automatically return to normal. This device can prevent the CMOS device from causing the so-called "thyristor triggering" phenomenon when encountering strong impact interference. This phenomenon refers to the substrate of the integrated circuit silicon chip becoming conductive, causing the current to increase, causing the CMOS integrated circuit to heat up or even burn out.

　　4. Lightning protection devices

　　For single-chip computer systems used outdoors or power lines and signal lines that are introduced from the outdoors to indoors, the lightning protection of the system must be considered. Common lightning protection devices include: gas discharge tubes, TVS (Transient Voltage Supervention), etc. When the power supply voltage of the gas discharge tube is greater than a certain value, usually tens of volts or hundreds of volts, the gas breaks down and discharges, and the strong impulse pulse on the power line is introduced into the ground. TVS can be regarded as two parallel Zener diodes in opposite directions, which are turned on when the voltage at both ends of the circuit is higher than a certain rated value. Its characteristic is that it can pass hundreds or even thousands of amperes of current in a transient state. This type of component should be used in conjunction with inductors that are resistant to common mode and differential mode interference to improve the anti-interference effect.