Analog Switches in Programmable Analog Devices: Quiescent Defective Behaviours

Analog Switches (AS) play an essential role in a large number of Mixed-Signal circuits. Depending on the use of AS, designers have optimised their topology to meet the needs of each specific switching function. Furthermore, the success of Field Programmable devices in the digital domain (FPGAs) has motivated some manufacturers to explore similar solutions to fast prototype in the Analog and Mixed Signal domains. In this work, we explore the defective behaviours of programmable AS under realistic catastrophic and parametric defects. A classification of the DC defective behaviours for bridging and open defects is presented. This classification shows that the simple fault model with faulty state of permanently transistor “stuck-on” or “stuck-off” is not sufficient to reflect the real behaviour of a defective switch. It has also been found that parametric defects such as threshold voltage variations are not DC testable, and would therefore require additional AC tests.