In electronic design, the most commonly encountered technology is the circuit board grounding, from the most common single analog circuit loop ground, a simple digital circuit loop ground to analog digital circuit hybrid ground, from the ground way all show The development of electronic design. If you have other requirements for the design of the product, such as EMC testing, circuit board signal frequency is relatively high (the signal rise time of 10ns or even lower order of magnitude), then, need to consider the grounding technology but also meet this the elements of. So, today to analyze the grounding technology under these factors.

Before analyzing the grounding technology of the circuit board, first of all to understand a reason, grounding technology is to improve the stability of the circuit one of the factors. In the circuit design, through a variety of grounding technology to reduce the loop, is one of this method. It is now simply to reduce the impact of the loop to take the technology.

A uses optocoupler to connect the circuit

In the design of the circuit, in order to fully protect the post-circuit circuit to avoid the impact of the previous circuit, optocoupler isolation technology is one of the commonly used methods. This design, can be a good way to reduce the impact of the circuit to accept the circuit, it is precisely because the introduction of optocoupler, greatly reducing the impact of the loop on the circuit.

B using isolation transformer technology to connect the circuit

This method uses a 1: 1 transformer, which isolates the transmit and receive circuits. So that the receiving circuit of the ground circuit greatly reduced.

C using common mode choke

In the circuit design, the receiving circuit through the common mode choke coil and the transmission circuit connected, so that the circuit can greatly reduce the circuit, but also for the receiving circuit EMC testing to provide good technical support.

D using balanced circuit technology

In this method, the transmission circuit is usually a multi-point parallel power supply, through the corresponding parallel to the module circuit, the final parallel in parallel with each module single point grounding. In the balanced circuit, the current flow of each module does not affect each other, thereby improving the stability of the system.

Introduce the method of reducing the ground loop, now introduced in order to reduce the grounding of various methods.

First, floating technology

In the electronic design, one of the commonly used methods is the floating technology, the circuit of this method of the signal and the external public is not connected, thus ensuring a good circuit isolation. The circuit is well isolated from the external system and is less susceptible to interference from the external system. However, it is easy to accumulate static electricity on the circuit to produce electrostatic interference, which may cause dangerous voltage. Small low-speed (<1mhz) equipment can be used to work floating (or work to single-point metal shell), metal shell single point of the earth.

Second, the series of single-point grounding

This grounding method is recommended by the company Daniel a grounding method, because of its simple, in the circuit board design do not pay attention to so much, so will use more. However, this circuit is prone to co-impedance coupling, so that each circuit module interacts with each other.

Third, the parallel single point grounding

This method of grounding, although out of the series of single-point grounding common impedance coupling problem, but in actual use, will introduce too much ground wire bother, as to what kind of need in the actual process of comprehensive evaluation. If the board area allows, use the parallel mode, if you keep the connection between the various circuit modules is simple, then the use of series mode. In general, the downloaded board has power modules, analog circuit modules, digital circuit modules and protection circuit modules, in which case I use a parallel single point grounding method.

Four, multi-point grounding

Multi-point base technology in the daily design will be used in the multi-module circuit design used more, this grounding method can effectively reduce the high-frequency interference problem, but also prone to the design of the loop problem , This design should take full account of this point, improve the stability of the system design. Small high-speed (> 10MHz) equipment should work with its metal chassis to achieve multi-point grounding, grounding point spacing should be less than the maximum operating frequency of 1/20, and the metal shell single point of the earth.

In short, in the electronic circuit design, the most important point is to reduce the circuit circuit area, which improve the electronic design stability and improve the electronic system EMC design has an important role. In the actual design, through the comprehensive evaluation of the above various technologies, through the use of flexible, in order to achieve the purpose of improving system stability.