A methodology and design for effective testing of voltage-controlled oscillators (VCOs)

In this paper, a cost-effective DFT solution for the testing of ring oscillator-based VCOs is presented. The strategy is based on the reconfiguration concept: we propose to modify the circuit so that the VCO operates as a digital structure in test mode. The test can then be performed on a standard digital tester, avoiding the use of costly mixed-signal test equipment. In addition, simulation results show that the use of an adequate digital test strategy permits one to obtain better fault coverage than a classical functional center frequency test