Graduation Year


Document Type




Degree Granting Department

Electrical Engineering

Major Professor

Wilfrido Moreno, Ph.D.


Clocked Storage Elements, Logical effort, Spice simulations, Power consumption, Clocked logical units


This dissertation presents a new systematic approach to flip-flop design using Internal Clock Gating, (ICG), and Adaptive Body-Bias, (ABB), in order to reduce power consumption. The process requires careful transistor resizing in order to maintain signal integrity and the functionality of the flip-flop at the target frequency.A novel flip-flop architecture, based on the Transmission Gate Flip-Flop, (TGFF), which incorporated ICG and ABB techniques, was designed. This architecture was simulated intensively in order to determine under what conditions its use is appropriate. In addition, it was necessary to establish a methodology for creating a standard testbench and environment setup for the required Hspice simulations. Software tools were written in C++ and Perl in order to facilitate the interface between Cadence Design Tools and Hspice.The new flip-flop, which was named the Low-Power Flip-Flop, (LPFF), was compared to the Transmission-Gate Flip-Flop, (TGFF), and to the Transmission-Gate with Clock-Gating Flip-Flop, (TGCGFF). Comprehensive Hspice simulations of the three flip-flop designs, implemented with Bsim3v3 transistor models for TSMC 180 nm technology, were used as the means of comparison.Simulations demonstrated that the new flip-flop is appropriate for applications that require low switching activity. In such a situation the LPFF consumes 7.8% to 95.7% less power than the TGFF and 0.8% to 23.7% less power than the TGCGFF. Power savings obtained by the LPFF increase as the length of the period with no switching activity increases, especially when the input data is all zeros. The trade-off is an increase in the D-to-Q delays and in the flip-flop area. The LPFF presented D-to-Q delays of 60% to 69% longer than the delays of the TGFF and 9% to 11% longer than the delays of the TGCGFF. The LPFF cells require an area that is 15% to 34% larger than the TGFF cells and 6% to 17% larger than the TGCGFF cells.