Gabriela Peretti

Oscillation Test Strategy: A Case Study

In this paper is proposed as a case study the test of a folded cascode operational amplifier using the Oscillation Test Strategy (OTS). This Operational Amplifier (OPA) is chosen in order to evaluate the ability of OTS to test a more complex amplifier than those previously reported. To obtain comparative results, three different types of single-OPA oscillators are employed.A catastrophic-fault injection procedure is carried out using SPICE. In all oscillators, simulation results show that the fault coverage obtained is lower than those previously obtained by many researchers for simpler amplifiers. This fact suggests that OTS might be inconvenient for applications using the OPA targeted in this work and requiring high fault coverage.

Exploring the Ability of Oscillation Based Test for Testing Continuous -Time Ladder Filters

In this work, we present an exploratory study on the ability of oscillation-based test (OBT) for testing continuous-time low-pass ladder filters. Particularly, fifth and seventh order Butterworth and elliptic filters are addressed. We devote our effort in determining the efficiency of OBT for detecting deviation-faults in the filters components, using signal-flow graphs for modeling the filters. For implementing the OBT oscillators, we use non-linear elements in the feedback paths. The describing function approach is adopted for the mathematical treatment of the nonlinear elements. Additionally, the oscillation conditions are established with a very good precision using Bode plots. For characterizing our OBT schemes, we inject arbitrary deviation-faults and then establish the fault coverage. An alternative approach is also suggested in the paper, based in the assessment of the lowest deviations in each circuit parameter able to be detected using the proposed oscillators. In this way, it is possible to determine the hard-to-verify components

Oscillation-Based Test in OTA-C filters: A case study

In this work, we explore the ability of oscillation-based test (OBT) for testing OTA-C filters. Adopting a second-order band pass filter as a case study, we present a scheme that uses a non linear characteristic in the feedback loop. The effectiveness of the strategy is qualified by means of fault simulation.

A low-cost configurability test strategy for an embedded analog circuit

This paper proposes a configurable test strategy for an embedded analog configurable circuit (EACC) composed by operational amplifiers and interconnection resources that are present in the MSP430 microcontroller family from Texas Instruments®. The test strategy is particularly useful for in-field application requiring reliability, safe operation or fault tolerance characteristics. The strategy minimizes the cost in hardware overhead by employing only the hardware and software resources of the microcontroller. Our test proposal consists in programming all EACC configurations and testing its functionality by measuring only a few parameters. The processor executes an embedded test routine that sequentially programs the configurations, acquires data from an ADC channel and performs required calculations. The test strategy is experimentally evaluated using commercial hardware provided by the vendor. Our experimental results show very good repeatability, with errors below the expected.

OBT implementation on an OTA-C band-pass filter

In this work, we explore the ability of OBT for testing OTA-C filters with a more complex OTA configuration than in previously reported one. Adopting a second-order structure as a case study, we use a non-linear block in the feedback loop in order to force the oscillations. The evaluation of the test quality is made by fault simulation. The simulation results show that the filter present very good fault coverage values.

An adaptive amplifier system for wireless sensor network applications

This paper presents an adaptive amplifier that is part of a sensor node in a wireless sensor network. The system presents a target gain that has to bemaintained without direct human intervention despite the presence of faults. In addition, its bandwidthmust be as large as possible. The system is composed of a software-based built-in self-test scheme implemented in the node that checks all the available gains in the amplifiers, a reconfigurable amplifier, and a genetic algorithm (GA) for reconfiguring the node resources that runs on a host computer. We adopt a PSoC device from Cypress for the node implementation. The performance evaluation of the scheme presented is made by adopting four different types of fault models in the amplifier gains. The fault simulation results show that GA finds the target gain with low error, maintains the bandwidth above theminimum tolerable bandwidth, and presents a runtime lower than exhaustive search method.

Quality Assessment of Transient Response Analysis Method for Detecting Radiation-Induced Faults

We evaluate the ability of transient response analysis method (TRAM), a simple test strategy proposed for filters, to detect deviations in circuit specifications beyond established limits. Particularly, we focus our attention on deviations produced by displacement damage in integrated resistors. This damage is produced by the impact of high-energy particles like the encountered in space environments. For this purpose, we formulate a simple deviation-fault model that takes into consideration the degradation addressed. Additionally, more transient response parameters are taken into account in order to improve the fault coverage. We adopt for our evaluations two typical second-order filters as cases of study. For these filters, the simulation results show that TRAM reaches excellent fault coverage for both filters, suggesting that its use in space applications is encouraging.

Estimating the quality of Oscillation-Based Test for detecting parametric faults

This paper proposes a new performance characterization for Oscillation-Based Test (OBT). The ability of OBT for detecting deviation faults under simultaneous statistical fluctuation of the non-faulty parameters is evaluated. For this purpose, we use Monte Carlo simulations and a fault model that considers as faulty only one component of the filter under test while the others components adopt random values obtained from their fault-free statistical distributions. The new data reported here show (for the filters under study) the presence of hard-to-test components and low fault coverage values for small deviation faults.

Testing digital low-pass filters using oscillation-based test

In this paper, we propose a novel low-cost BIST scheme for testing low-pass FIR and IIR filters, based on the oscillation-based test (OBT). The OBT-BIST scheme developed here avoids test-pattern generation and tests the filter at-speed, without test-point insertion. We employ a systematic procedure for designing the oscillator and for obtaining the oscillation conditions in advance. The simulation results show high fault coverage for the filters under test, with low area overhead and acceptable test time.

An operational amplifier model for evaluating test strategies at behavioural level

This paper proposes a new operational amplifier model for evaluating test strategies at behavioural level. Major modifications on a previously reported model for improving its performance and for allowing reliable fault simulations are presented here. The new model presents a set of very appealing characteristics for behavioural-level fault injection and simulation. The matching between the behavioural-level model and a transistor-level one is evaluated for validating the model. We suggest the use of the model early in the design process, when the schematic of the circuit is not available for the test engineer and only the specifications are given. The model is also useful for evaluating different test alternatives for commercial operational amplifiers or standard cells designed by others vendors. The paper addresses two application examples and shows the usefulness of the model for evaluating test strategies when only the specifications of the circuit are available.