Best Practices in Schematic Capture

Schematic Capture is fundamental to the design process. The schematic capture environment is a CAD-like design interface in which graphical symbols of circuit components (such as op-amps, resistors, transistors, processors etc…) are placed and connected together to form a design topology (as seen in Figure 4).

Figure 4 - Schematic Capture

 In a schematic the design is represented in the form of symbols (in the ASCII and DIN standard) connected together by wires (called nets).  Nets are the second fundamental element of a schematic (after parts) and connect individual components into an actual design.

Every schematic begins with the selection and placement of components, and as a result an engineer’s initial task is to search their capture tool’s database for specific components. Many traditional EDA tools are lumbered with disorganized databases that are difficult to navigate. In these tools, component selection is a hurdle in the design process. In Multisim, all 17,000 components in the master database are logically organized into easy-to navigate groups . These groupings reflect the type of device and functionality, so that components such as diodes are in one group, while op-amps populate a separate analog group. This logical organization mirrors the way most manufacturers present their own parts libraries, providing an intuitive interface that an engineer has encountered many times before.

Inherently the design process is quite involved as an engineer continuously navigates to the database, searches for and picks a part, and then wires it into the design. In many traditional EDA tools, an engineer will quickly realize that wiring requires them to repeatedly switch betweenplacement and wiring modes for each new component and wire to be placed. In Multisim (figure 5), this tedium is eliminated by a modeless environment, where the mouse cursor’s proximity to pins and other connectors will automatically allow the drawing of wires. The ability to quickly create connections without constantly switching between drawing modes makes the capture process much more efficient.

Figure 5 - The NI Multisim Schematic Capture Environment