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.
Transient Rail Collapse
Supply Failure
Severe momentary drops in local supply voltage can cause logic gates to enter indeterminate states or trigger circuit resets. A transient rail collapse occurs when the power distribution network cannot provide enough current to satisfy a sudden spike in demand. This event is often caused by the simultaneous switching of a large number of high-power components.
Collapse Dynamics
Analysis of the power grid identifies the specific areas that are vulnerable to these rapid voltage drops. During a transient rail collapse, the local voltage can fall well below the minimum operating threshold for the transistors, leading to a loss of data or a system crash. Engineers use high speed simulation tools to model the interaction between the logic activity and the power distribution network.
The results guide the placement of additional capacitors and the reinforcement of the power traces. Verification includes checking the effective series resistance of the decoupling network to ensure it can respond to fast current spikes.
System Recovery
Prevention of these failures is necessary to ensure the reliability of the electronic system. If a transient rail collapse is detected during testing, the design must be modified to improve the power delivery or to reduce the peak current demand. Final validation involves stress testing the circuit under maximum load conditions to confirm that the voltage remains stable.