Analog checkers with absolute and relative tolerances

Abstract

The design of checkers aimed at the concurrent test of analog and mixed-signal circuits is considered in this paper. These checkers can on-line test duplicated and fully differential analog circuits. The test approach is based on exploiting the inherent redundancy of these circuits which results in the use of a code for the analog signals. The analog code is monitored by the checkers. An error signal which complies with existing digital self-checking parts is generated in the case that a code fails out of the valid code space. For the verification of the analog codes, absolute tolerance margins and tolerance margins which are made relative to signal amplitude are considered. A test pattern generator for off-line testing of the checkers is proposed

Design of self-checking fully differential circuits and boards

“…2. This is possible since analog codes can also be defined, for example the differential and duplication codes [15]. A tolerance is required for checking the validity of an analog functional circuit, and this is taken into account within the analog code.…”

Design of a window comparator with adaptive error threshold for online testing applications

“…A window comparator with relative error threshold voltage is described in [15]. It uses switched-capacitor circuit techniques and dynamically adjusts the comparator error thresholds by taking advantage of CMOS switch channel charge injection effects.…”

“…This implementation employs differential input pairs as preamplifiers, and use inverters to digitize the outputs of the pre-amplifiers. Comparator implementations in [14,15] are based on folded-cascoded op-amp circuits. Asymmetric differential pairs are intentionally used at the input stages of the op-amps to introduce input offset voltage, which is translated into the comparator error threshold.…”

A Programmable Window Comparator for Analog Online Testing

“…In the first category [10,11,12,13,14,15,16,17,18], the error threshold of a window comparator is constant regardless of its input signal levels. This type of window comparators quickly lose their faultdetection capabilities when signals being monitored become small.…”