Low-power pipelined phase accumulator with sequential clock gating for DDFSs

A pipelined phase accumulator (PACC) for direct digital frequency synthesisers (DDFSs) is presented. A highly pipelined structure is inevitable in a PACC design to achieve high-speed performance, which causes a large number of pre-skewing flip-flops (F/Fs) and leads clock signals to be a large source of power dissipation. Since the input data do not change every single cycle, clock gating can save power by decreasing the number of unnecessary clock switching in the pre-skewing F/Fs. Sequential clock gating for pipelined PACCs is proposed. Compared with the conventional pipelined PACCs with and without clock gating, the proposed scheme reduces power dissipation by up to 55.4 and 77.2%, respectively, for the 32-bit 8-pipelinestage PACCs.