Efficient C_eff model for gate output slew computation in early synthesis

摘要

A slew-based effective capacitance (C_eff) is used to compute gate output slew during early synthesis of an integrated circuit design. A π model is constructed for the gate and reduced to two parameters which are used to compute a slew value for the model, given a slew definition. A capacitance coefficient is then calculated as a function of this slew value. The effective capacitance is the product of the coefficient and the total capacitance of the π model. The output slew of the gate may in turn be computed using the slew-based C_eff. The coefficient may be computed by iteratively solving an equation representing output voltage over time dependent on the first and second parameters, by directly solving a closed-form equation which is a function of the first and second parameters, or by looking up the capacitance coefficient in a table indexed by the first and second parameters.