A BIST scheme for the detection of catastrophic faults in analogue functions

The widespread use of mixed analogue/digital circuits has added another dimension to the problem of testing VLSI circuits, namely that of testing, cost effectively, the analogue sections of a design. Unless the analogue functions can be tested efficiently, that is with good fault coverage and minimal overhead, the overall reliability of the device/system will be compromised. The factors which make analogue circuits more difficult to test than digital circuits are:- differing opinions on the classes of faults to be considered, ie catastrophic or parametric; there is no universal fault model for analogue faults, as in digital circuits-this makes test pattern generation and fault simulation extremely difficult; analogue testing is specification driven; and analogue designs are less structured. To overcome the problems of testing analogue circuits, a BIST scheme is proposed which is based on the indirect impulse testing technique. The overheads which would be incurred by the complete implementation of the technique, however, prohibits its use in VLSI circuits, consequently a simplified version of the technique has been considered and its fault detection capabilities examined