Voltage island circuit placement

摘要

A voltage island is disclosed. The voltage island comprises a physical domain and a lower voltage supply rail within the physical domain. The voltage island also includes an upper voltage supply rail within the physical domain. The physical domain is coupled to the appropriate voltage supply rail to ensure reverse biased junctions. Accordingly, a system in accordance with the present invention allows circuit placements associated with multiple voltage islands within a common circuit row or even adjacent circuit rows to be utilized in which the area effectiveness is greatly improved. The use of common Nwell biasing connected to the higher power supply ensures no forward biased junctions and allows butted circuit placement in cases where the other circuit physical constraints permit. This configuration will minimize the density loss associated multiple voltage island implementations.