Wakeup Scheduling in MTCMOS Circuits Using Successive Relaxation to Minimize Ground Bounce

Power gating is a very effective technique to reduce the subthreshold leakage by using sleep transistors to turn off the functional blocks or cells when they are not used. When the sleep transistors are turned on, the power grid may experience a huge current surge which may violate the integrity of the power grid. This paper addresses this problem by formulating the wakeup scheduling of sleep transistors as an exact mixed integer linear program (MILP). Since the resulting MILP is NP-hard, we propose a very efficient yet near optimal algorithm by successively relaxing the MILP to a sequence of linear program (LP) problems. The results obtained on the ISCAS benchmarks indicate that our proposed algorithm obtains a near optimal solution with a speedup of 15× on average compared to the MILP. The proposed algorithm has a runtime complexity which is linear in practice.