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Interlocked pipelined CMOS (IPCMOS), a new asynchronous set of clock circuits suitable for high-frequency and low-power operation, is described. In IPCMOS, the reduced power results from enabling the local clocks only when there is an operation to perform and from a simple single-stage latch. The single-stage latch can be used because the locally generated clocks driving adjacent stages are not enabled simultaneously. The combination of enabling the clocks only when there is an operation to perform and the simple latch can lower power by a factor of five to ten times in many applications. In IPCMOS, the staggered local clocks also result in a significant reduction of dynamic Ldi/dt noise. In addition to the locally generated interlocked clocks and the single-stage latch, unique circuits that combine the function of a static NOR and an input switch are key to achieving high performance and minimizing the overhead in the interlocking. In a 0.18-μm bulk CMOS technology, these circuits drive a path through a typical 64-b multiplier stage at 3.3-4.5 GHz on an experimental chip. IPCMOS also provides a way to implement the interface between asynchronous and synchronous portions of a design, thereby giving the approach a great deal of flexibility by making it possible to drop IPCMOS into portions of an existing synchronous design.
Date of Publication: Apr 2003