KSim: a stable and efficient RKC simulator for capturing on-chip inductance effect

On-chip inductance extraction is difficult due to the global effect of inductance, and simulating the resulting dense partial inductance matrix is even more difficult. Furthermore, it is well known that simply discarding smallest terms to sparsify the inductance matrix can render the partial inductance matrix indefinite and result in an unstable circuit model. Recently a new circuit element, K, has been introduced to capture the global effect of inductance by evaluating a corresponding sparse K matrix. However, the reason that K has such local properties is not clear, and the positive semi-definiteness of the corresponding sparse K matrix is not proved. In this paper, we present the physical interpretation of K. Based on the physical interpretation, we explain why the faraway mutual K can be ignored (locality) and prove that after ignoring faraway mutual K, the resultant K matrix is positive definite (stability). Together with a RKC equivalent circuit model, the locality and stability enables us to simulate an RKC circuit directly and efficiently for real circuits. A new circuit simulation tool, KSim, has been developed by incorporating the new circuit element K into Berkeley SPICE. The RKC simulation matches better with the full partial inductance matrix simulation with significant less computing time and memory usage, compared to other proposed methods, such as the shift-truncate method.