Discussing the Electromagnetic Compatibility Design of Single Chip Microcontrollers from PCB Design

 Factors affecting EMCVoltage: 

1.The higher the power supply voltage, the greater the voltage amplitude, resulting in more emissions, while low power supply voltage affects sensitivity.

2. Frequency: High frequencies generate more emissions, while periodic signals generate more emissions. In high-frequency microcontroller systems, a current spike signal is generated when the device is switched on and off; In a simulation system, a current spike signal is generated when the load current changes.

3. Grounding: Among all EMC issues, the main issue is caused by improper grounding. There are three signal grounding methods: single point, multi-point, and mixed. When the frequency is below 1MHz, a single point grounding method can be used, but it is not suitable for high frequencies; In high-frequency applications, it is best to use multi-point grounding. Mixed grounding is a method of single point grounding for low frequencies and multi-point grounding for high frequencies. The grounding layout is crucial, and the grounding circuits of high-frequency digital circuits and low-level analog circuits should not be mixed.

4. PCB design: Proper wiring of printed circuit boards (PCBs) is crucial for preventing EMI.

5. Power supply coupling: When the device switches, transient currents are generated on the power line, which must be attenuated and filtered out. Transient currents from high di/dt sources cause ground and trace "emission" voltages, while high di/dt generates a wide range of high-frequency currents that excite components and cable radiation. The changes in current flowing through the wire and inductance can cause a voltage drop, and reducing the changes in inductance or current over time can minimize this voltage drop.