Ground is to study the potential of the system design. The first time starting from the conceptual design review, it should be made into a product. Important principles grounded: to maintain and isolation
Were grounded analog circuits and digital circuits is the easiest, most effective way possible to suppress noise. The layer or layers of PCB is typically dedicated to the ground. If the designer is not very serious, it will be directly connected to the analog circuit and the ground plane. After analog and digital circuits return network table is returned in the same network. Automatic router appropriate response, and is connected to all ground together, creating a vicious failure. Must be separated and each one is connected to the ground plate with the analog circuit. This leads to a passive element in the huge headstone and floating IC head surface mounting plate.
Other grounding principles:
Due to the distributed capacitance of capacitors and coupling means, the ground plate and the power must be on the same potential. So it will be an independent power tablet is very important.
Do not put the digital and analog flat flat piled up. The analog power, ground and analog ground coincide with the digital power piled up. If any portion of the analog and digital plates overlap capacitance and high speed noise superimposed literacy coupled to the analog circuit portion, which is isolated against the plate Fig.
And isolation does not mean that the system is electrically isolated. They must agree on a common potential in general on a single low-impedance point. System connection method is generally only a ground terminal, if the AC power supply system, it is the safety ground terminal, and that the DC power supply system is a battery ground. All others will flow back to the client. Related to the development of a circuit is not all flow back to the same ground of discipline would be a good idea. All flows back line should be connected together at a single point, this is a single point grounding system. Souls
Some ground is chassis. By connecting multiple chassis to avoid grounding circuit is very important. Ensure that only one aspect of a system designed for the chassis ground is the most difficult.
If possible, use separate pins in a separate return, the return line is only connected to the grounding system. Aging and repeated connections make contact with the connector pin is the resistance increases. Therefore, a plurality of pins is necessary. Most word is composed of many layers PCB negatives and thousands of network composition. Adding a network is not a problem, but increase the number of connector pins to die. If the connector pins are not increased, then the line in the specialized preventive measures, the two return to a single network on the PCB board is very necessary.
Hold the digital signals to isolate portions of the analog circuit is very important. Planar isolation is meaningless. Keeping analog lines simple analog circuits such as over there near the high-speed digital lines passing through sensitive, must be carefully placed passive components. Digital signal lines must be built around analog circuitry, not the analog ground and power planes overlap. If not, the design will include a new broadcast radio schematic! Most digital clock frequency is very high, so that in a small capacitance between the line and the plane can be coupled to a large noise. Remember, he is not only a question of fundamental frequency caused by the TV clock, but also high-frequency harmonics of the fundamental frequency.
As in the analog circuit I / O flat nearby is a very good way. Digital Designer for high current integrated circuit (IC) is a 50 Mill 1 (mil) they think reducing the resistance of the line to get rid of the noise, the fact that they do is to create a long, small capacitors, the capacitor The coupled noise from digital ground and power board into a speaker, which makes the problem even worse!
