SymBIST: Symmetry-Based Analog and Mixed-Signal Built-In Self-Test for Functional Safety

Abstract

We propose a Built-In Self-Test (BIST) paradigm for analog and mixed-signal (A/M-S) Integrated Circuits (ICs), called symmetry-based BIST (SymBIST). SymBIST exploits inherent symmetries in an A/M-S IC to construct signals that are invariant by default, and subsequently checks those signals against a tolerance window. Violation of invariant properties points to the occurrence of a defect or abnormal operation. SymBIST is designed to serve as a functional safety mechanism. It is reusable ranging from post-manufacturing test, where it targets defect detection, to on-line test in the field of operation, where it targets low-latency detection of transient failures and degradation due to aging. We demonstrate SymBIST on a Successive Approximation Register (SAR) Analog-to-Digital Converter (ADC). SymBIST features high defect coverage, short test time, low overhead, zero performance penalty, and has a fully digital interface making it compatible with modern digital test access mechanisms. Index Terms-Analog and mixed-signal integrated circuit testing, built-in self-test, design-for-test, defect-oriented test, defect simulation, on-line test, concurrent error detection.

BIST-Assisted Analog Fault Diagnosis

“…The central idea in SymBIST [16], [17] is to build invariant signals (or invariances) by monitoring internal nodes. An invariance is defined as a signal with a constant value irrespective of the input.…”

“…Finally, since the invariances hold true for a running input, SymBIST can be reused for on-line concurrent error detection during normal operation [17].…”

“…We use the same case study, i.e., a 10-bit SAR ADC IP by STM, employed in [16], [17]. Herein, we reintroduce the case study in Sections IV-A-IV-F for the purpose of completeness.…”

“…In error-free operation, V o is a DC signal with value A + G • c. A defect will shift the DC component of V o and/or will add an AC component, causing V o to slide outside the tolerance window [δ − , δ + ], and raising the output from 0 to 1. The switches are used to disconnect the checker when SymBIST is disabled or to set the checker into self-test mode so as to verify its operation before it is used for diagnosis [17].…”

“…We opt for using generic BIST virtually applicable to any analog IC class, such that the BIST-assisted diagnosis paradigm is also generic. Our starting point is the recently proposed generic Symmetry-based BIST (SymBIST) [16], [17], which has been demonstrated for defectoriented post-manufacturing test and on-line test. Herein, we demonstrate how SymBIST can be utilized for fault diagnosis too.…”