An efficient and automated algorithm for placing power gating switches
within a voltage island of an integrated circuit, which ensures
compliance with defined electrical specifications. A power gating switch
is placed in every legal location on the integrated circuit and the
minimum number of power gating switches is calculated based on current
requirements of the voltage island. Each power gating switch is modeled
as an ideal resistor whose value is obtained from the slope of the I-V
curve of the switch when operating in the linear region. The power
distribution networks of the integrated circuit and the voltage island
are extracted and modeled as a resistive network. Circuit macros placed
within the voltage island are modeled as current sources. The extracted
linear network is then simulated using a DC stimulus to obtain expected
voltage drops across the voltage island as well as the currents in all
branches of the voltage island power grid and through each power gating
switch. The process iterates until a placement of a minimum number of
power gating switches is found that guarantees compliance with the
electrical specifications.