Mixed circuit testing is known to be a very difficult task. This is due to the difficulty of: testing the analog part of the circuit, controlling the digital signal from the analog outputs, observing the analog outputs in the digital circuit, controlling the analog circuit from the digital outputs and observing the digital signals in the analog circuit. As a solution to these problems, we propose an automatic test vector generation for mixed circuits to perform functional testing. In this paper, a case of an analog block followed by a digital block is considered. The experimental results (simulation and discrete realization) show the efficiency of the automatic test generation technique.