11.2. Component Library Overview

11.2. Component Library Overview

A component library is composed of one or more components. Generally the components are logically grouped by function, type, and/or manufacturer.

A component is composed of:

• Graphical items (lines, circles, arcs, text, etc ) that provide the symbolic definition.
• Pins which have both graphic properties (line, clock, inverted, low level active, etc ) and electrical properties (input, output, bidirectional, etc.) used by the Electrical Rules Check (ERC) tool.
• Fields such as references, values, corresponding footprint names for PCB design, etc.
• Aliases used to associate a common component such as a 7400 with all of its derivatives such as 74LS00, 74HC00, and 7437. All of these aliases share the same library component.

Proper component designing requires:

• Defining if the component is made up of one or more units.
• Defining if the component has an alternate body style also known as a De Morgan representation.
• Designing its symbolic representation using lines, rectangles, circles, polygons and text.
• Adding pins by carefully defining each pin’s graphical elements, name, number, and electrical property (input, output, tri-state, power port, etc.).
• Adding an alias if other components have the same symbol and pin out or removing one if the component has been created from another component.
• Adding optional fields such as the name of the footprint used by the PCB design software and/or defining their visibility.
• Documenting the component by adding a description string and links to data sheets, etc.
• Saving it in the desired library.