An oscillation-based built-in test scheme with AGC loop W. Toczek * Metrology and Electronic Systems Department, Faculty of Electronics Telecommunications and Informatics, Gdansk University of Technology, Narutowicza 11/12, 80-952 Gdan´ sk, Poland Received 2 January 2006; received in revised form 18 April 2006; accepted 20 June 2006 Available online 4 July 2006 Abstract The paper validates Oscillation-Based Built-In Test (OBIT) scheme for testing the analog portion of mixed-signal sys- tem assembled on a printed circuit board. This scheme uses both frequency and time domain measurements in order to maximize the fault coverage. Some aspects of implementation of the OBIT that comprises transformation of the circuit under test to an oscillator and designing of a measuring system, is presented. Special attention is being paid to the devel- opment and analysis of the oscillation-based test structure with an automatic gain control (AGC) loop. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Build-in testing; Oscillation-test method; Test structure with AGC 1. Introduction A recent metrological advance is the art of designing circuits with the Build-In Test (BIT) or Build-In Self-Test (BIST) feature. This approach has emerged as one of the most important testing techniques at the current time [1–3]. An Oscillation-based Build-In Test technique (OBIT) relies on converting the Circuit Under Test (CUT) into an oscillator. Many researchers have promoted oscillation-based measurements for some years. The method based on an oscillator circuit has been proposed in [4] to estimate the ratio of the sec- ond pole to the gain-bandwidth product of matched operational amplifiers. Forcing the fast comparator to oscillate in order to test for voltage offset has been suggested in [5]. Formulation of the general idea of the fault-oriented oscillation-test methodol- ogy and justification throughout examples such as amplifiers, filters and analog-to-digital converters was firstly reported by Arabi and Kaminska in [6– 10]. The idea consists on measurement of the oscil- lation waveform parameters (frequency, amplitude, etc.) that are related to the component values. Therefore, changes of the parameters from their nominal values indicate faults in the CUT. The oscillation approach has been applied to test the digitally programmable switched-current biqua- dratic filters [11] and switched-capacitor filters [12– 14]. In [15] the use of OBIT technique is proposed to test the configurable analog blocks of the Field Programmable Analog Arrays. In [16] the enhance- ment of the fault locating capability has been reached by the combinational testing approach, consisting of oscillation-based tests, power supply 0263-2241/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.measurement.2006.06.007 * Tel.: +48 583471657; fax: +48 583472255. E-mail address: toczek@eti.pg.gda.pl Available online at www.sciencedirect.com Measurement 41 (2008) 160–168 www.elsevier.com/locate/measurement