Distributed Delay-Based BIST for Mixed-Signal Circuits in Flexible Electronics

Flexible electronics (FE) based on indium gallium zinc oxide thin-film transistors (IGZO-TFTs) are emerging for ultra-low-power wearable applications. However, lack of packaging, limited pins, and high device variability make conventional Automatic Test Equipment (ATE) impractical for testing analog/mixed-signal circuits in FE. This work presents a dualpurpose ring oscillator (RO) and voltage-controlled oscillator (VCO) serving as functional timing blocks and core structures for a distributed delay-based BIST framework. The oscillators achieve 1100× area reduction and 5600× lower power than previous IGZO-TFT designs. Lightweight digital BIST embedded within each RO stage enables stage-wise delay monitoring for defect detection. The BIST achieves 93% defect coverage for individual defects and 88% for multiple simultaneous defects, with only 3% power overhead and no external test equipment.