On-Chip Evaluation of Oscillation-Based-Test Output Signals for Switched-Capacitor Circuits

This work presents a simple and low-cost method for on-chip evaluation of test signals coming from the application of the Oscillation-Based-Test (OBT) technique. This method extracts the main test signal features (amplitude, frequency and DC level) in the digital domain requiring just a very simple and robust circuitry. Experimental results obtained from an integrated chip demonstrate the feasibility of the approach. 1.INTRODUCTION Testing embedded building blocks is much more difficult than testing their stand-alone counterparts, and usually this cannot be done by replicating conventional test techniques. In mixedsignal ICs, the most affected components are the analog cores, since analog testing is based on checking functional specifications, which can be conflictive when the test time has to be kept short, the number of available pins is reduced (as it normally happens in SOCs) and full access to input/ output core terminals cannot be granted. Furthermore, functional test techniques greatly differ depending on the involved analog components, making it almost impossible to define a general (functional) test methodology applicable to any analog block. Additionaly, mixed-signal testers need to cope with demanding requirements of speed, accuracy and memory storage, which means a high cost. As a consequence, analog cores play a crucial role in the feasibility of a complex system, and their market appeal depends on the development of test strategies that can be used in very different application environments.