Optimization of Resistances in RL Snubbers for Power Distribution Network of Integrated Circuits

Resonance of parasitic impedances in power distribution network (PDN) can increase leakage of the simultaneous switching noise current from integrated circuits (ICs) in the radio frequency (RF) range. The leaking SSN current is a major possible source of the conducted electromagnetic interference (EMI). A method have been proposed to control the PDN resonance by inserting a parallel RL circuit, RL snubber, to damp the resonance. In the previous work, the optimal resistance of the RL snubbers had been determined based on an equivalent circuit of PDN where equivalent series inductances (ESLs) on package had been neglected. In this work, the equivalent circuit was improved as the ESLs on package were taken into account because they were comparable to those on-board and not negligible. A method determining the optimal resistance was also improved. The RL snubbers were applied with the improved optimal resistance to a typical PDN. Effects of the RL snubbers in reducing the RF power current and in improving the power integrity were demonstrated in circuit simulations. Results of the demonstration confirmed that the improved method for optimal resistance gives more EMI reduction and better PI than the method in the previous work.