High Speed Dual Mode Logic Carry Look Ahead Adder

A novel high speed Carry Look Ahead Adder (CLA) is presented. The proposed CLA is implemented using Dual Mode Logic (DML) methodology, as recently introduced by our group. DML allows dynamic switching between static and dynamic modes of operation. In static mode, the DML gates feature very low power dissipation with moderate performance, while in dynamic mode they achieve higher performance, albeit with increased power dissipation. The proposed CLA utilizes this powerful ability of DML by a dynamic selection of critical paths according to the input vectors. The chosen critical paths are operated in the dynamic mode and improve the CLA delay. The rest of the CLA operates in the DML static mode, improving CLA power consumption. A 32 bit DML CLA was designed in a 40nm low power TSMC process. Simulation results showed 45% gain in speed and 70% in power dissipation, when compared to the CMOS and dynamic CLAs, respectively.