Abstract
This paper describes a design for testability technique for second-order bandpass operational transconductance amplifier and capacitor (OTA-C) filters using an oscillation-based test topology. The oscillation-based test structure is a vectorless output test strategy easily extendable to built-in self-test. The proposed methodology converts filter under test into a quadrature oscillator using very simple techniques and measures the output frequency. Using feedback loops with nonlinear block, the filter to oscillator conversion techniques easily convert the bandpass OTA-C filter into an oscillator. With a minimum number of extra components, the proposed scheme requires a negligible area overhead. The validity of the proposed method has been verified using comparison between faulty and fault-free simulation results of Tow-Thomas and KHN OTA-C filters. Simulation results in 0.25 $$\upmu $$ m CMOS technology show that the proposed oscillation-based test strategy for OTA-C filters is suitable for catastrophic and parametric faults testing and also effective in detecting single and multiple faults with high fault coverage.
Highlights
Test and diagnosis techniques for digital systems have been developed and universally implemented during the last three decades
Oscillation based test has been seldom considered for bandpass filters in the literature, so in this work we describe a low-cost Oscillation-based test (OBT) scheme for bandpass OTA-C filters with two filter to oscillator conversion methods
We have proposed a vectorless, dynamic Design for testability (DFT) method for OTA-C filters, based on converting the filter under test into an oscillator using minor modifications in the original filter circuits
Summary
Test and diagnosis techniques for digital systems have been developed and universally implemented during the last three decades. Based on reconfiguration of original circuit to oscillator, [24] proposed a built-in self-test circuit for testing analogue and mixed-signal circuits and considered the proposed solution on testing the typical benchmark circuit of second-order active filter. In [26], diagnosis based on OBT was implemented by creating fault dictionary and running artificial neural networks as classifiers These works were based on the presumption that the amplifying elements within the circuit under test (CUT) perform ideally. Using an on-chip Schmitt trigger as the frequency reference, [28] applied the oscillation-based built-in self-test (OBIST) strategy to low-pass and high-pass analogue filters designed in 0.35μm and 90nm CMOS technologies respectively. Application of the oscillator-based DFT scheme to two integrator loop Tow-Thomas and KHN biquads are presented, because these structures are commonly used individually as filters and as building blocks for high order filters.
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