Modeling Dynamic Parasitic Loading Effects on Scan Network Timing Margins
Dynamic parasitic extraction during ATPG shift prevents false timing violations by accounting for state-dependent capacitance and power rail collapses.
FinFET Dynamic Load
Current Demand
Transient current demands placed on the power grid by multi-gate transistors vary according to the switching frequency and transition patterns of the device. Because of the high drive strength of these devices, a finfet dynamic load can cause noise on the local supply rails during rapid logic switching. The analysis focuses on the interaction between the transistor geometry and the distribution of current through the narrow fin structures.
Load Assessment
Characterization involves measuring the peak and average currents drawn during transitions under different capacitive loading conditions. In a complex integrated circuit, the finfet dynamic load is modeled as a time-varying current source that reflects the internal state of the logic gate. Designers use these models to size the power distribution network and to place local decoupling capacitors.
The three-dimensional nature of the fin means that thermal considerations also play a role in how the load affects performance over time. Simulation tools account for the specific capacitance of the gate fins to predict the switching speed of the transistor.
System Performance
Managing these electrical demands is necessary to prevent localized overheating and voltage instability. When a finfet dynamic load exceeds the capacity of the local power grid, the resulting voltage drop can slow down signal transitions and reduce the noise margin of the circuit. Final verification ensures that the power delivery system can support the maximum possible switching activity without violating the reliability limits of the silicon.