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.
Setup Slack Degradation
Timing Erosion
Reductions in the timing margin available for a signal to stabilize before a clock edge increase the risk of functional failure in synchronous circuits. Various factors contribute to setup slack degradation, including increased interconnect resistance, supply voltage drops, crosstalk, and thermal effects. When the slack becomes negative, the circuit can no longer operate at the target clock frequency.
Erosion Causes
Analysis of the timing paths identifies the specific components that contribute to the loss of margin over different operating corners. In high speed designs, setup slack degradation is often driven by the increasing complexity of the logic and the impact of parasitic capacitances. Engineers use aging models and environmental simulations to predict how these margins will change over the life of the product.
Corrective actions include optimizing the logic to reduce the number of gate levels or using higher drive-strength cells. Static timing analysis tools track these changes to ensure that the design remains functional at high temperatures.
Performance Limit
Verification of the final sign-off ensures that every path maintains a positive slack value under the worst-case conditions. An excessive amount of setup slack degradation can limit the maximum operating speed of the device. The final report provides a detailed view of the timing margins for all critical paths to confirm the integrity of the design.