minDensity

Specifies the minimum metal density required for the layer, as a percentage from 0 to 100. The constraint can be given as a fixed value that applies to the entire design, or as a table of values that apply to areas of the design, as you step through them, and are based on the step size.

The maxDensity constraint is used in conjunction with the minDensity constraint to ensure that the metal density is neither too dense nor too sparse.

minDensity Quick Reference

Constraint Type	Layer
Value Types	FltValue, Flt1DTblValue
Database Types	Design, Technology
Scope	design, foundry
Category	Density

Value Types

minDensity constraints have the following value types:

• FltValue
  Specifies the minimum percentage of the design area that the metal on the specified layer may occupy over the entire area. The density percentage is calculated as the metal area divided by the total design area. Valid values: 0 to 100
• Flt1DTblValue
  The lookup key (“step”) represents the step size and the value represents the minimum density percentage for a check window. Check windows are square with equal height and width.
  • If windowStepSize is not given, the check window dimensions are 2*step size.
  • If windowStepSize is given, the window size that corresponds with the given step size is used.
  
  Density checking starts with the check window in a corner of the design, then the check window is moved across the design incrementally, by step size, each time validating that the density percentage in the check window is greater than or equal to the minimum allowed percentage.
  
  

Parameter

• windowStepSize (OneDTblValue, optional) The lookup key (“step”) represents the step size and the value represents the window size. This table is used only when minDensity is a Flt1DTblValue to look up the window size associated with a given step size.

Examples

• Fixed Value
  Sets the minimum Metal2 density to 50%.
  

  Format	Example
  Tcl	set_layer_constraint -constraint minDensity \ -layer Metal2 -Value 50.0
  LEF	LAYER Metal2 MINIMUMDENSITY 50.0 ;
  Virtuoso	spacings ( ( minDensity "Metal2" 0.50) )

• 1D Table: Index step size
  Sets the minimum Metal2 density based on the step size of the check window.
  

  Format	Example
  Tcl	set_constraint_parameter -name windowStepSize -row_name window \ -OneDTblValue { 60 120 120 240} -row_interpolation snap_down \ -row_extrapolation {snap_up snap_down} set_layer_constraint -constraint maxDiffDensity -layer Metal2 \ -Flt1DTblValue {60 20.0 120 25.0} -row_interpolation snap_down \ -row_extrapolation {snap_up snap_down} -row_name step
  Virtuoso	spacingTables( ( minDensity "Metal2" (( "step" nil nil "window" nil nil)) ( ( 60.0 120.0 ) 20.0 (120.0 240.0 } 25.0 ) ) ) ;spacingTables

Related Topics

Density Constraints

Return to top