maxDensity

Specifies the maximum percentage of the total design area the metal in the specified layer may occupy (density = metal layer area/total design area). 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 minDensity constraint is used in conjunction with the maxDensity constraint to ensure that the metal density is neither too dense nor too sparse.

maxDensity Quick Reference

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

Value Types

maxDensity constraints have the following value types:

• FltValue
  Specifies the maximum 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 maximum density percentage for a check window. Check windows are square with equal height and width.
  • If windowStepSize is not given, the check windows 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 less than or equal to the maximum 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 maxDensity is a Flt1DTblValue to look up the window size associated with a given step size.

Examples

• Fixed Value
  Sets the maximum Metal2 density to 70%.
  

  Format	Example
  Tcl	set_layer_constraint -constraint maxDensity \ -layer Metal2 -Value 70.0
  LEF	LAYER METAL2 MAXIMUMDENSITY 70.0 ;
  Virtuoso	spacings ( ( maxDensity "Metal2" 70.0) )

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

  Format	Example
  Tcl	set_layer_constraint -constraint maxDensity \ -layer Metal2 -Flt1DTblValue {50 70.0 100 75.0}
  Virtuoso	spacingTables( ( maxDensity "Metal2" (( "step" nil nil )) ( 50.0 70.0 100.0 75.0 ) ) ) ;spacingTables

Related Topics

Density Constraints

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