Design Definitions
While library definitions capture generic component properties, design definitions capture how those components are used in specific assemblies.
From Library to Design
The transition from library to design involves:
Select a library component - Choose a component from the library
Instantiate in the assembly - Place the component in the design
Assign connectivity - Connect the component’s terminals to nets
Apply constraints - Add design-specific constraints (spacing, impedance, etc.)
Validate - Check the design against rules
Design Definition Entities
Key entities in a design definition:
product_definition - The specific design view
shape_definition_representation - The geometric data for this design
design_context - The context in which the design is created
assembly_component_usage - How components are used in the assembly
Design Data
Design-specific data includes:
Placement data - Exact position and orientation of each component instance
Routing data - How traces connect between component pads
Layer assignments - Which layers each feature occupies
Design rules - Rules that apply to this specific design
Requirements - Specific requirements for this design instance
Example: Surface Mount Resistor on a PCB
For a 10kΩ 0402 resistor placed on a PCB:
Library definition - 0402 package outline, two terminals, 10kΩ resistance
Design definition - Placed at (x=12.5, y=7.3, z=0.0) on top layer, rotated 90°
Connectivity - Terminal 1 connected to Net "VCC", Terminal 2 connected to Net "SIGNAL_1"
Constraints - Minimum 0.15mm clearance to adjacent components