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Collection of Classic Technical guidelines: circuit Simulation and PCB Design

This article is about "Classic Technical Guide Collection: circuit Simulation and PCB Design". This article mainly explains some analysis and classic cases of circuit simulation and pcb design, which can bring convenience to everyone's study and facilitate understanding. If there is anything you don't understand, you can add a group to understand: 613377058.

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Brief introduction of electromagnetic compatibility (EMC)

The performance of analog circuits is often adversely affected by the high-frequency signals generated by nearby electrical activities. In addition, devices with built-in analog circuits may also adversely affect their external systems. Reference 1 (page 4) gives the definition of "electromagnetic compatibility (EMC)" according to the definition of IEC-60050:

EMC refers to the ability of a device, a complete set of equipment or a system to maintain good performance in the electromagnetic environment without introducing a large amount of electromagnetic interference to any device, equipment or system in the environment.

Therefore, the term "EMC" describes two aspects:

1. The ability of electrical and electronic systems to maintain normal operation without interfering with other systems.

two。 The ability of such systems to work as expected in a rated electromagnetic environment.

Therefore, the complete EMC guarantee will show that the equipment under design should neither produce stray signals nor be affected by out-of-band external signals (i.e. those outside the target frequency range). Most of the time, analog devices suffer from the latter kind of EMC problems. This section will focus on how to properly deal with this kind of spurious signals.

Externally generated electrical activities may produce noise, which is called "electromagnetic interference (EMI)" or "radio frequency interference (RFI)". The following will discuss EMI from two aspects of electromagnetic interference and radio frequency interference. For simulation designers, one of the more challenging tasks is to properly control the equipment to prevent bad operations caused by EMI. It is important to note that in this case, EMI and / or RFI are usually harmful. Once inside the equipment, it can and will cause a decline in the performance of the equipment, and usually has a considerable impact.

This section focuses on how to minimize the poor analog circuit operation caused by the receipt of EMI/RFI signals.

Such bad behavior, also known as "EMI or RFI sensitivity", indicates the tendency of the device to behave abnormally when exposed to EMI/RFI. Of course, there is also the complementary EMC problem, that is, about stray "radiation". However, compared with high-speed logic, analog circuits usually involve less pulse-driven high-speed, high-current signal edges (that is, the signal edges that produce such spurious signals), so this aspect of EMC is not emphasized here. In any case, readers should note that this may be important, especially when analog circuits and high-speed logic work together to form a mixed-signal environment.

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