Variation-Aware Circuit Macromodeling and Design Based on Surrogate Models - Simulation and Modeling Methodologies, Technologies and Application - page 246

Fig. 1. Circuit performance modeling
Automatic Modeling Flow. In this work, we constructed an automatic modeling flow
that is able to generate performance models from transistor-level circuit simulations,
as shown in Fig. 2. Before the modeling starts, a set of input and output parameters
are defined. The modeling techniques are also configured, including the model tem-
plate, adaptive sampling strategy, and accuracy measurement. An accuracy target is
defined as well. At the beginning of the modeling process, a small set of initial sam-
ples are generated. Then transistor-level SPICE simulations are performed using this
initial set, and the corresponding responses are collected and used as the modeling
data. Surrogate models are then constructed and their parameters optimized. The
model accuracy is measured and the optimization continues until only negligible im-
provements can be made by changing the model parameters. If the desired accuracy is
not reached, the adaptive sampling is evoked to add a new set of samples. The process
continues until the fit reaches the targeted accuracy. When the process finishes, the
model expressions are be exported and used in the follow design steps.
Fig. 2. Automatic adaptive performance surrogate modeling flow