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# Retarded Time Domain Circuit Simulation Algorithm for Interconnect Analysis

IP.com Disclosure Number: IPCOM000108486D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 55K

IBM

## Related People

Heeb, H: AUTHOR [+2]

## Abstract

Disclosed is an algorithm for the faster simulation of circuits of the type that arise in the modeling of high performance interconnects. The rapid increase in the cycle time of new computers leads to very fast rising pulses on the interconnects and the wires in the chips. Due to these fast pulses, the time of flight becomes significant and cross couplings between interconnect elements must be retarded. As a consequence, cross-couplings over distances greater than the distance of action, given by the simulation time-step used in the time domain simulator, decouple.

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Retarded Time Domain Circuit Simulation Algorithm for Interconnect Analysis

Disclosed is an algorithm for the faster simulation of
circuits of the type that arise in the modeling of high performance
interconnects.  The rapid increase in the cycle time of new computers
leads to very fast rising pulses on the interconnects and the wires
in the chips.  Due to these fast pulses, the time of flight becomes
significant and cross couplings between interconnect elements must be
retarded.  As a consequence, cross-couplings over distances greater
than the distance of action, given by the simulation time-step used
in the time domain simulator, decouple.

In our algorithm, capacitive and inductive cross-couplings
between interconnect elements are retarded (delayed) according to the
correct speed V of the interaction using a history mechanism for the
voltage or current at every circuit node.  The maximum time step of
the circuit simulation is limited to TMAX.  Any two interconnect
elements further apart than DMIN = TMAX*V are totally decoupled for
any time-step and we can guarantee that they are independent  because
they couple to the voltage or current of the other element in in an
earlier time-step. This voltage or current is independent of the
current state of the circuit and can be treated as constant source.

In the dielectric media used for high performance packages,
objects more than 1 cm apart decouple for a maximum time-step of