This paper describes a practical test approach for analog-to-digital converters (ADCs) based on the oscillation-test strategy. The oscillation-test is applied to convert the ADC under test to an oscillator. The oscillation frequencies are able to monitor the ADC conversion rate, differential nonlinearity (DNL) and integral nonlinearity (INL) at each quantization band edge (QBE). Using this method, no analog stimulus should be supplied and therefore the need for a costly precision signal generator is eliminated. Besides, as the oscillation frequency is evaluated using pure digital circuitry, test accuracy is increased. This test approach is not limited to a special kind of ADC. Simulations and practical implementation prove the efficiency of the proposed test approach for ADCs. 1 Introduction Analog-to-digital converters (ADCs) are the most frequently encountered mixed-signal circuits. ADCs are precision products and their test requires reference circuits with at least two more bits ...

Parametric faults are a significant cause of incorrect operation in analog circuits. Many design for test techniques for analog circuits are ineffective at detecting multiple parametric faults because either their accuracy is poor, or the circuit is not tested in the configuration in which it is used. We present a design for test (DFT) scheme that offers the accuracy needed to test high-quality circuits. The DFT scheme is based on a circuit that digitally measures the ratio of a pair of capacitors. The circuit is used to characterize the transfer function of a switched capacitor circuit, which is usually determined by capacitor ratios. In our DFT scheme, capacitor ratios can be measured to within 0.01% accuracy and filter parameters can be shown to be satisfied to within 0.1% accuracy. With this characterization process, a filter can be directly shown to satisfy all specifications that depend on capacitor ratios. We believe the accuracy of our approach is at least an order of magnitude...

Design-for-test modifications of different types of active RC filter stages for the oscillation-based testing are proposed. Additional switches or a feedback loop network are employed. The first solution offers the possibility of a simple built-in test implementation while the second is more applicable to the use of an external tester.