Magic Blue Smoke


Power Gating and Decoupling Cap cell insertion(Cont’d)


Continuing on the same topic, here are are some thoughts on the insertion criteria


if planning for decoupling cap in the power planning stage, a good strategy would be, to add as many decoupling cap as possible in the permanent power network at the positions close to the switch cells for maximum effectiveness and to minimize its impact on wakeup latency and rush current.  If possible integrating the decoupling cap into the switch cell will simplify the decoupling cap cell  insertion to a greater extent. The maximum capacitance of the decoupling cap on the permanent power network is constrained by the leakage and area penalties.

To fix dynamic IR-drop violations in post-layout stage, it is recommended to add decoupling cap to the permanent power network close to the violation spots, if the violations are related to the permanent power network. Rest of the violations can be fixed by adding decoupling cap to the virtual power network closer to the hot-spots.