Schematic Capture in Electronic Design
Introduction
Schematic capture is an essential phase in electronic design automation (EDA). It involves using eCAD (Electronic Computer-Aided Design) tools to draw schematics which include electronic symbols, wires, and other graphical symbols to represent electrical and electronic circuits. The schematic serves as a blueprint for laying out a PCB (Printed Circuit Board) and guides engineers in the subsequent design phases, from component placement to routing to manufacturing.
Common eCAD Tools
Professional
Altium Designer: A high-end tool offering robust features for professional circuit design, PCB layout, and simulation.
Cadence Allegro Design Entry HDL: Another professional-grade tool known for its robustness and industry-wide acceptance.
Free
Kitcad: A free tool suitable for hobbyists or those who are just getting started with PCB design.
Eagle: Also a free tool, it is popular among students and DIY electronics enthusiasts.
Design Overview
Setup a Project Using the eCAD Tool
The first step in using an eCAD tool is to set up a new project. This typically involves specifying the type of project, the files to include, and the settings specific to the design tool.
Setup Common Libraries
Libraries contain symbols and footprints for commonly used components. Setting up libraries can simplify the design process and ensure consistency across projects.
Create Symbols and Footprints
During the design process, it may be necessary to create custom symbols and footprints for components not available in the common libraries.
Translate System Architecture into Schematic
After the initial setup, the next step is to translate the system architecture into a schematic. This involves placing components, connecting them with wires, and possibly adding notes or other designators.
Export Net List for Layout
Once the schematic is complete, a netlist is exported. This file contains information about how components are connected, and it serves as an input for the PCB layout stage.
Typical Design Gates in the Context of Product Development Process
Schematic Lock
After the schematic has been reviewed and approved, it is "locked" to prevent further changes, thus moving the project to the next design phase.
Placement Lock
After components have been placed on the PCB layout and reviewed, the design is again "locked" to proceed to routing.
Design for Manufacturability (DFM)
After the routing is complete, the design undergoes a DFM review to ensure that it can be manufactured efficiently and reliably.
Finalizing Fabrication File
Once DFM reviews are complete, and any necessary adjustments are made, the design files are finalized and sent to the PCB manufacturer for fabrication.
Conclusion
Schematic capture is a critical phase in EDA, providing the roadmap for all subsequent design steps. The choice of eCAD tools and adherence to design gates significantly influence the project's success. By understanding each stage in detail, engineers can produce designs that are not only functional but also manufacturable.