Mentioned in this article for the design of electromagnetic interference we mainly from the aspects of hardware and software design process, below is from the PCB chip design to the software to introduce the processing of electromagnetic compatibility.

A, effect of EMC factor

1: the higher voltage power supply voltage, the larger the mean voltage amplitude,emission is more, and the low supply voltage sensitivity.

The 2 frequency: high frequency to produce more emission, periodic signal generatingmore emission. In high frequency in single chip microcomputer system, produce current spikes when the device switches; in the simulation system, produce current spikeswhen load current changes.

3 ground: in all EMC in the title, the main topic is the ground due to improper. There are three kinds of signal grounding methods: single point, multiple and mixed. Atfrequencies below 1MHz, can adopt the method of single point grounding, but not suitable for high frequency; in high-frequency applications, the best use of multi point grounding. Mixed grounding is the low frequency with single point grounding, multipoint grounding method with high frequency. Wire layout is the key of digital circuit,high frequency and low level analog circuit grounding circuit cannot be mixed.

4.PCB design: printed circuit board (PCB) appropriate wiring to prevent EMI is essential.

5 power to coupling: when switching, on the power line can produce a transient current, must attenuation and filter out these transient current. The transient current from the high di/dt source causes and stitch "launch" voltage, high frequency currenthigh di/dt produce a large range, the actuating member and the cable radiation. Thecurrent flowing through the wires and inductance change will cause the pressure drop,decreasing the inductance or current variation with time can make the minimum pressure drop.