Using real-world examples the book features: Clear discussions, without complex mathematical analysis, offlux minimization concepts Extensive analysis of capacitor usage for variousapplications Detailed examination of components characteristics with variousgrounding methodologies, including implementation techniques An in-depth study of transmission line theory A careful look at signal integrity, crosstalk, andtermination Author by : John S. Figure 14: A possible coupling problem. In fact, the current flowing in the plane generates a magnetic flux that wraps around the plane. In this case, the source would be the signal source and the antenna would be the trace-plane pair. If we view the two cables as parts of an antenna and represent the antenna current path by an antenna impedance, illustrated in Figure 13 c , it becomes apparent that the currents flowing in the microstrip trace circuit induce a voltage across the plane that drives one cable relative to the other. This voltage drives the surface of the component relative to the surface of the board as indicated by the model in Figure 12 b.
Remember also, that loop area is generally more important than trace length. The best design is the one that meets all of the specifications with the lowest cost and highest reliability. Types of leaded package are relatively numerous, however passive components tend to stick to two form factors; axial or radial. One problem many suppliers of components and their customers alike have is knowing what information would be useful. Again, neither the board nor the heatsink is electrically small at the frequency of interest.
An example of this would be the least significant bit on a microprocessor address bus, since stepping through consecutive addresses can cause this signal to toggle at the clock frequency. The second routing strategy gaps the plane, but routes the trace over the gap. However, the capacitance between the surface of the component and the heatsink provides an indirect electric-field connection. The benefits are both technical and commercial, there is not only a requirement for suppliers to provide the data, but also for consumers to request the relevant data for their application. If a printed circuit board is laid out in a manner that minimizes the possibility of inducing a voltage between any two of these possible antenna parts, then it is much less likely to have a radiated emission or radiated susceptibility problem.
Figure 7: Which gap position affects the flow of the signal return current? Please click button to get emc at component and pcb level book now. Nevertheless, these traces are often the source of the most difficult radiated emissions problems. The omnipresence of communication systems, various electronic appliances and the use of ever increasing frequencies, all contribute to a noisy electromagnetic environment which acts detrimentally on sensitive electronic equipment. The board's metal planes are another potential antenna part. Which is the best choice? Clearly, high-frequency signals driven directly onto traces or other conductors need to be returned to their source on other conductors that are nearby to avoid radiated emissions due to direct conducted coupling between the source and the antenna. If the plane were to be gapped for any reason, as shown in Figure 7, a gap in position 2 would have little effect on the signal integrity or on radiated emissions.
These planes are usually named after the component pins they are connected to. This was achieved simply by placing the two connectors on the same side of the board. Narrowband, high-frequency analog signals can be particularly difficult to work with. How do high-frequency currents and voltages appear on low-frequency data lines? Analog Signals Analog signals can be broadband or narrowband, high frequency or low frequency. Circuits of particular interest are discussed below.
We should also reorient the components to minimize the length of the traces. The separation between any two power planes on a given layer should be at least 3 mm. Figure 1: A printed circuit board. In this figure, we see that the currents injected onto some of the low-speed address lines are nearly as strong as the currents in the clock signal. Potential antenna parts are the three connectors. This site is like a library, you could find million book here by using search box in the widget. Select active digital components that have maximum acceptable off-chip transition times.
Readers will obtain an overall picture of dependability from failure causes to countermeasures for their relevant systems or products, and therefore, will be able to select the best choice for maximum dependability. It should also be much more apparent which design guidelines are most important and which are not important at all for a specific design. If the design has more than one ground plane layer, then any connection to ground at a given position should be made to all of the ground layers at that position. However, these same guidelines applied to other designs with no concept of where they came from or why they work can result is wasted effort and non-functional boards. Digital Clock Circuits Synchronous digital circuits employ a system clock that must be sent to every active component on or off the board that needs to interpret the digital signal.
Power switching noise can always be reduced by slowing down the transition time of the switching circuit. Note that we could have provided pads for mounting filter components on the phone lines if we felt that might be necessary. Noise and frequency analysis on fundamental electromagnetic signals, noise, and transforms is explained. Most poor designs are the direct result of neglecting to consider where the signal currents were likely to flow. It will also help to promote an efficient layout, since the active devices are unlikely to require two different voltages at any one position on the board. Two printed circuit board layouts.