64-bit pipeline conditional carry adder with MTCMOS TSPC logic

In this study, a 64-bit 8-stage pipeline conditional- carry adder (CCA) with the Multi-Threshold voltage CMOS (MTCMOS) TSPC logic for power-aware applications was designed and verified. The 64-bit pipeline CCA needs 4 cycles only. Transistors on critical paths use a low threshold voltage to increase the operation speed. Other transistors use a normal threshold voltage to save power. Compare with single normal threshold voltage TSPC schemes, the proposed pipeline scheme has a higher operation frequency and better power-frequency ratio. Furthermore, the circuit style of proposed multiplexer can be extended on high-speed FPGA or pass-transistor logic (PTL). The simulations show that the 64-bit CCA with MTCMOS TSPC can be operated on 2.4GHz and its power / maximal frequency ratio is 43.9 muW/MHz.