Delay Efficient 32-Bit Carry-Skip Adder

The design of a 32-bit carry-skip adder to achieve minimum delay is presented in this paper. A fast carry look-ahead logic using group generate and group propagate functions is used to speed up the performance of multiple stages of ripple carry adders. The group generate and group propagate functions are generated in parallel with the carry generation for each block. The optimum block sizes are decided by considering the critical path into account. The new architecture delivers the sum and carry outputs in lesser unit delays than existing carry-skip adders. The adder is implemented in 0.25 mu m CMOS technology at 3.3V. The critical delay for the proposed adder is 3.4 nanoseconds. The simulation results show that the proposed adder is 18% faster than the current fastest carry-skip adder. Copyright (C) 2008 Y. S. Lin and D. Radhakrishnan.