Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
2001-09-14
2003-07-01
Siek, Vuthe (Department: 2825)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C716S030000, C716S030000, C716S030000
Reexamination Certificate
active
06587989
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to electrical data processing, and more particularly to systems for circuit design and analysis of modular components. It is anticipated that primary application of the present invention will be in the design of application specific electrical data processing systems.
BACKGROUND ART
Briefly, when laying out a printed circuit board (PCB) using a software tool, such as ALLEGRO, PADS, or OrCAD, each component needs to be modeled with a footprint and a definition of the component pins. However, when a subassembly, such as a daughter card, has needed to be part of the design, the associated connectors have had to be placed individually, and the physical constraints manually designed and checked. Not only can this be a long and tedious process, but it must be repeated for every new design using the same subassembly. Clearly this existing process is time consuming and repetitive, and each time it is repeated there is an opportunity for mistakes to be made.
PCB design is a complex subject, as a summary of conventional practice the following covers it at three levels. First, the general usual steps are stated, then these are individually discussed, and finally some key aspects from the first two levels are further discussed in detail.
A typical board design project includes the general steps of: creating the board, specifying parameters for it, placing and checking the component placements, routing and checking the routings, and finishing the board. Thus, at a top level, the complex topic of PCB design can be reduced to four steps.
To create the board a netlist is created from a schematic design using a capture tool. The netlist may particularly include design rules to guide the later logical placement and routing. To specify board parameters, global settings are provided for the board, including units of measurement, grids, and spacing. In addition, a board outline can be created and the layer stack, padstacks, and vias can be defined. To place components, and to check this, a component tool is used to manually place components on the board individually or in groups. The placements can then be checked using information from a variety of sources. To route the board, and to check this, a routing tool is used to manually route. Many such tools today include push-and-shove capabilities, which move tracks to make room for a track or tracks currently being routed. The routing can then also be checked using routing information from a variety of sources. To finish the board a layout tool is used, having an ordered progression of command options to use. For example, in OrCAD these commands include Design Rule Check, Cleanup Design, Rename Components, Back Annotate, Run Post Processor, and Create Reports. A layout tool may also include or interface with full-featured CAD and CAM tools.
Even at this second level, PCB design may not seem overly daunting. The problem, however, is the shear volume of data that must be managed, and the interrelationships between that data. It is this which has motivated the growth of a substantial industry providing software tools and even recent university text books on computer aided PCB design and fabrication.
A netlist file is used to describe the interconnections of a schematic design using the names of the nets, components, and pins. A netlist typically contains: footprint names; electrical packaging; component names; net names; the component pin for each net; and net, pin, and component property information.
A technology template may be used to specify the characteristics of a board, including manufacturing complexity and component type. Technology templates can also include the layer structure, grid settings, spacing instructions, and a variety of other board criteria.
A board template may also be used. This combines a board outline and possible mounting holes, edge connectors, and other physical board objects which may be merged with a layout tool's default technology template.
Finally, a board file is generated which contains all of the board's physical and electrical information. In view of the complexity of many PCB designs today, these files and templates may be quite large. In fact, the amount of data that software design tools can handle has become a major criteria for their selection and pricing, and the desired operation speeds and other capacity issues similarly have become criteria for selecting the hardware on which these software tools are run.
There are basically two ways to create a PCB, to start from scratch or to use a previously created template. In many tools one can also import information from CAD tool files, but this approach presumes that these files were once also created from scratch or based on templates, at some point. Thus, ultimately, somebody has to start from scratch.
After establishing a schematic as a starting point, when designing a new PCB, or a template to be used in, potentially, a number of PCB designs, the design process tends to next focus on components. Most PCB design tool sets today include a librarian tool, to handle component information, and these often come or can be configurably ordered with a large database of information on standard components. This component database is often termed a component information system (CIS) and it may contain information that is used at all levels of the design process. A typical CIS today includes logical and physical component data, as well as purchasing and manufacturing data.
The CIS or PCB library “content” is often modified considerably by the library users. PCB library users may add additional components to the library. This can be done often by buying new library content from the original tool provider, and “subscription” schemes for this are common. Component manufacturers are also a frequent source for new library content, particularly for non-standard components. Component distributors are also playing an increasing role here, supplying component library definitions for common software tools to their prospective customers, to facilitate the customers design with and hopeful purchase of the respective components. Lastly, the end users of PCB libraries may modify or add component definitions themselves. For instance, an engineer may change a component definition based on past experience with that component, say its noise or heat characteristics, or a purchasing agent may change order lead times based on past experience or a distributor's promise. A PCB library user may also add their own component definitions. For simple components this is widely done. For instance, a component such as a micro processor may be developed in-house or may be so new that its manufacturer has not yet standardized and shipped a library component definition.
PCB designers are comfortable with library component definitions, they have the qualities of basic building blocks, the available tools work well with them, and they tend to be well tested and reliable. Modern PCB designs, however, tend to quickly become more complex than simply picking and placing collections of basic component elements. Templates, macros, modules, and hierarchical design logic (HDL), are sub-tools which most sophisticated PCB design tools today include in at least some form, although with varying levels of acceptance and actual utility to the end users.
Templates are widely used. For example, if a designer is working on a PCB that will fit into a standard physical package, they can store the basic physical data for the board in a template file. If it is foreseeable that the next generations of the product will use, say, TTL ICs, the designer may go ahead and include a power supply and even clock circuits. If there are changes in future designs those will usually be minor in these areas. For very common PCBs, such as motherboards and daughter boards for personal computers, the PCB design tool provider may even supply very basic standard templates. Thus, PCB designers are often relatively comfortable with templates.
PCB designers, however, tend to not b
Rosenbaum Alan
Rosenfeld Paul I.
Ampro Computers, Inc.
IPLO -Intellectual Property Law Offices
Roberts Raymond E.
Siek Vuthe
Tat Binh
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