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

2026-07-21

AI Summary

This work addresses the challenges of effectively testing analog/mixed-signal circuits in flexible electronics, which are hindered by the absence of packaging, limited pin availability, and high device variability that render conventional automatic test equipment inadequate. The authors propose a lightweight built-in self-test (BIST) framework based on distributed delay monitoring, innovatively repurposing ring oscillators (ROs) and voltage-controlled oscillators (VCOs) as dual-function units serving both as functional timing modules and test cores. Implemented for the first time in IGZO-TFT-based flexible circuits, this approach achieves a dual-purpose oscillator with 1,100× reduced area and 5,600× lower power consumption, integrated with a compact digital BIST structure. The solution attains 93% coverage for single defects and 88% for multiple concurrent defects, with only a 3% power overhead.

Abstract

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 dual-purpose 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 1100x area reduction and 5600x 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

Problem

• Flexible Electronics
• Mixed-Signal Circuits
• Testing
• Device Variability
• Limited Pins

Innovation

• distributed delay-based BIST
• IGZO-TFT
• ring oscillator
• mixed-signal testing
• flexible electronics