The existing decoupling capacitance optimization approaches meet constraints on input impedance for package. In this paper, we show that using impedance as constraints leads to large overdesign and then develop a noise driven optimization algorithm for decoupling capacitors in packages for power integrity. Our algorithm uses the simulated annealing algorithm to minimize the total cost of decoupling capacitors under the constraints of a worst case noise. The key enabler for efficient optimization is an incremental worst-case noise computation based on FFT over incremental impedance matrix evaluation. Compared to the existing impedance based approaches, our algorithm reduces the decoupling capacitor cost by 3x and is also more than 10x faster even with explicit noise computation.
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