Fast Power- and Slew-Aware Gated Clock Tree Synthesis

Abstract—Clock tree synthesis plays an important role on the total performance of chip. Gated clock tree is an effective approach to reduce the dynamic power usage. In this paper, two novel gated clock tree synthesizers, power-aware clock tree synthesizer (PACTS) and power- and slew-aware clock tree syn-thesizer (PSACTS), are proposed with zero skew achieved based on Elmore RC model. In PACTS, the topology of the clock tree is constructed with simultaneous buffer/gate insertion, which reduces the switched capacitance. In PSACTS, a more practical clock slew constraint is applied. Compared to previous works, clock tree synthesis is done first and followed by the insertions of clock gates. The clock slew changes a lot after the insertions of clock gates in real cases. In our work, the clock tree is constructed simultaneously with the insertions of clock gates. This ensures the limitation of the clock slew can be strictly satisfied while the limitation of the clock slew is always applied in the real design. The experimental results show that the power cost of our work is smaller and the runtime is reduced. The slew rate constraint is satisfied with a small clock skew from SPICE estimation. Gener-ally, our work has better performance, improved efficiency and is more practical to be applied in the industry. Index Terms—Clock gating, clock tree synthesis, design automa-tion. I