The silent killer of analog reliability: Why SPICE misses floating net
This is a technical commentary article by Bhanu Pandey, a product engineer for Calibre Design Solutions at Siemens Digital Industries Software, addressing the 'floating net' structural defect in analog and mixed-signal (AMS) verification. Citing the most recent Wilson Research Group / Siemens EDA Functional Verification Study, the article states that first-silicon success rates have hit a historic low, with nearly 68% of designs requiring two or more spins, and that AMS verification remains a primary source of these re-spins. It explains how floating nets arise (a node disconnected from all low-impedance paths in power-down modes, its voltage determined by trapped charge on parasitic capacitances, drifting over time due to leakage currents, potentially causing latch-up or permanent physical damage) and lists three reasons SPICE simulation misses the defect: convergence artifacts (gmin stepping) that mask it, the time-scale problem, and testbench coverage limits. A case study of a design with an internally labeled 'VICTIM' net shows the defect was masked in simulation but in silicon caused a massive current spike that damaged the output stage, leading to a costly field failure and a subsequent re-spin. The article advocates automated structural analysis (e.g., the Calibre Insight Analyzer) to detect floating nets before fabrication and shift reliability verification left. It contains no pricing, supply-demand, capacity or procurement information and is background technical content.
- Impact score
- 10 / 100, low impact