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.
Power Distribution Network Impedance
Frequency Characteristic
Frequency-dependent resistance and reactance characteristics define how a circuit board maintains stable voltage levels under varying current loads. The power distribution network impedance determines the magnitude of voltage fluctuations that occur in response to transient current demands from the integrated circuits. A low impedance must be maintained across a wide frequency range to prevent noise from interfering with sensitive logic.
Network Analysis
Measurement involves using a vector network analyzer to characterize the response of the power and ground planes. To optimize power distribution network impedance, designers place multiple decoupling capacitors with different resonant frequencies in parallel. This creates a flat impedance profile that can handle both low frequency bulk current changes and high frequency switching noise.
Vias and trace widths are also sized to minimize the inductive and resistive components of the network. Proper plane stacking further reduces the overall loop inductance of the system.
Target Performance
Compliance with the power integrity specification is confirmed by comparing the measured impedance against a target value derived from the maximum allowable voltage ripple. If the power distribution network impedance exceeds this limit at any frequency, the circuit may experience intermittent failures or reduced timing margins. Final board designs are simulated and tested to ensure they provide a stable electrical environment for the mounted components.