Worst case voltage drops in power and ground buses of CMOS VLSI circuits
Kriplani, Harish
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https://hdl.handle.net/2142/20706
Description
Title
Worst case voltage drops in power and ground buses of CMOS VLSI circuits
Author(s)
Kriplani, Harish
Issue Date
1994
Doctoral Committee Chair(s)
Hajj, Ibrahim N.
Department of Study
Electrical and Computer Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Computer Science
Language
eng
Abstract
Currents flowing in the power and ground (P&G) buses of CMOS digital circuits affect both circuit reliability and performance by causing excessive voltage drops. Excessive voltage drops manifest themselves as glitches on the P&G buses and cause erroneous logic signals and degradation in switching speeds. Maximum current estimates are needed at every contact point in the P&G buses to study the severity of the voltage drop problems and to redesign the supply buses accordingly. These currents, however, depend on the specific input patterns that are applied to the circuit. Since it is prohibitively expensive to enumerate all possible input patterns, this problem has, for a long time, remained largely unsolved. In this thesis, we propose a pattern-independent, linear time algorithm (iMax) that estimates at every contact point, an upper bound envelope of all possible current waveforms that result from the application of different input patterns to the circuit. The algorithm is extremely efficient and produces good results for most circuits as is demonstrated by experimental results on several benchmark circuits. The accuracy of the algorithm can be further improved by resolving the signal correlations that exist inside a circuit. We also present a novel partial input enumeration (PIE) technique to resolve signal correlations and significantly improve the upper bounds for circuits where the bounds produced by iMax are not tight. We establish with extensive experimental results that these algorithms represent a good time-accuracy trade-off and are applicable to VLSI circuits.
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