Electrical & Computer Engineering
Master of Science in Electrical and Computer Engineering (M.S.E.C.E.)
Year Degree Awarded
Month Degree Awarded
interconnect, circuit, VLSI, current sensing, power reduction, temperature
Global on-chip interconnects in deep sub-micron CMOS present challenges in satisfying delay constraints in the presence of noise and dramatic temperature variations, while minimizing energy consumption due to leakage and static power. Although repeaters are typically used to reduce delay and maintain signal integrity in long interconnects, they introduce significant area, power (both dynamic and leakage), delay, noise and design overhead as well as exacerbating variations due to their local power supply noise and temperature. Current-Sensing is an alternative to repeaters that transfers signals with no intermediate circuits by sensing current rather than voltage at the end of a long interconnect. Among the current sensing circuits, Differential Current-Sensing (DCS), which uses conventional CMOS inverters to drive differential signal, is preferred because of its high common-mode noise rejection. The DCS circuit is fast and simple in layout compared to repeater insertion despite significant static and leakage power which remains a barrier for broad application. Temperature variation throughout the chip also causes the timing uncertainty on interconnects to increase.
This thesis addresses current-sensing interconnect circuit design in several aspects. First, it provides an improved differential current-sensing circuit called the differential leakage-aware sense amplifier (DLASA), that uses local power gating that results in 39.6% reduced leakage and static power compared to conventional differential current sensing. Secondly, thermal impact on interconnect is studied and temperature sensitivity is analyzed for interconnect circuits. Theoretical analysis is discussed as a base design guideline, then accurate simulation based experiments in 65nm, 45nm and 32nm CMOS technologies are used for verification from 25OC to 150OC. Thus this project provides a view of the year of technology toward 2013.
Wayne P. Burleson