Poorly done high speed boards can cost your company tremendous amounts of time and money due to regulatory failures, low manufacturing yields or warranty returns. High speed signals behave like RF signals so incorrect routing techniques can result real world fpga design with verilog pdf a multitude of tribulations. Comprehension of high speed issues and relevance of common design decisions and trade-off’s results in the best planning and greatest possible success for a high speed project.
Identify and prioritize the signals according to their requirements. Set budgets for SI, EMI and timing. Then analyze each signal type and determine layout rules that will enable that signal type to meet its budget. Determine a power method which can maintain the objectives. Perform a detailed look at termination, ground bounce, ringing, cross talk and EMI and analyze all of the routing needs to determine overall and individual buss rules that will result in a viable board. Route the board and simulate, simulate, simulate to validate that it will meet the budgets.
Do cross talk analysis to ensure nothing is being coupled causing EMI or other errors. Rely on our printed circuit board layout proficiency and be more confident in your design. Signal Integrity Did you know that the bulk of re-designs on digital boards are as a result of high speed issues? These issues can begin as digital noise contaminating the analog signals and flow on down in a domino effect to product or regulatory failure. Wireless Layout Radio Frequency or RF designs are often infamous as “black magic”. This belief exists because the fundamental mechanisms of how RF energy is developed within a printed circuit board is not well understood by many.
Many aspects of RF design are theoretical mathematical calculations. Digital and RF layout techniques can be quite different. One major difference is part placement. Typical digital designs are more forgiving about part placement than RF designs. Digital designs often place components in a similar fashion or orientation, as all vertical or horizontal based on 90 degree rotation increments.
RF designs many times use full 360 degree rotational increments so that components can be placed to follow circuit flow. Components are also placed so that there will be minimal lengths for tracing between components. Component pads may be butted up to each other for minimal distances. The lack of defined traces is another significant difference between RF and Digital layouts. RF will utilize globular copper shapes to connect component terminals instead of a defined trace between pads. Physical routes when used generally follow a strip-line or controlled impedance style for connections.
The use of shielding to contain spurious emissions is also a concern for RF boards. Ground planes can be used to act as image planes or as one side of a PCB-mounted shielded enclosure. PCB shielding is a noninvasive suppression technique that does an outstanding job of reducing both the radiated emissions and susceptibility of a circuit. The use of physical shielding as in radiation shells or cans is another method of containing un-wanted emissions.
Many other details must be factored in when doing RF layouts. Good design practices and knowledge can help to keep the bad aspects of that ole “Black Magic” from cropping up. RoHS Conversions Pb-free is having some effect on printed circuit board layouts. For Pb-free assemblies, one of the most important layout issues is the component’s physical footprint. It is important to determine whether or not components can resist the higher reflow temperatures needed in the lead-free process. These temperatures can be in excess of 250º or 260ºC. An assembly concern that needs to be considered is whether or not there are SMT components mounted on both sides of the board.
The components on the bottom may be glued and must be able to withstand solder temperature of over 250ºC. If they can not, a wave soldering fixture will be needed to shield them. Additionally, layer stackup and impedance control calculations change if the pcb laminate material is changed to be lead-free complaint. Microstrip, dual stripline or single-ended, these impedances ensure signals get to their destination with minimal crosstalk and as clean as possible so it is important to re-run the calculations on the new chosen material. 2005-2015 Advantage Electronic Product Development Inc. The designers of Verilog wanted a language with syntax similar to the C programming language, which was already widely used in engineering software development.
A Verilog design consists of a hierarchy of modules. Modules encapsulate design hierarchy, and communicate with other modules through a set of declared input, output, and bidirectional ports. This system allows abstract modeling of shared signal lines, where multiple sources drive a common net. A subset of statements in the Verilog language are synthesizable. Verilog was one of the first popular hardware description languages to be invented.