19 July 2013

.lib: Operating Conditions:


7.2.3.2. Operating Conditions:

This section models the environmental variations of IC. These are known as Process, Voltage, and temperature variations. In short it is called PVT.

 

A set of values of PVT is known as operating condition. A logic library is characterised for one set of operating condition. Generally there are different libraries specific to different operating condition. There are three operating conditions very commonly used in ASIC synthesis and implementation. Based on the affect on cell delay due to the variation in PVT these classifications are made.

They are:

Ø  worst (also called ‘max’ or ‘slow’)à library in which cells are characterised for maximum delay

Ø  best(also called ‘min’ or ‘fast’)àlibrary in which cells are characterised for minimum delay

Ø  nominal(also called ‘typical’ or ‘normal’)àlibrary in which cells are characterised for typical delay

Eg.:

  /* Operation Conditions */

  nom_process                     : 1.00;

  nom_temperature                 : 125.00;

  nom_voltage                     : 0.95;

 

  voltage_map (VDD,0.95);

  voltage_map (VSS,0.00);

 

  define(process_corner, operating_conditions, string);

  operating_conditions (slow) {

    process_corner : "SlowSlow";

    process       : 1.00;

    voltage       : 0.95;

    temperature   : 125.00;

    tree_type     : balanced_tree;

  }
  default_operating_conditions : slow;

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