A CMOS based logic driver design for a 16 × 16 multiplexer based read-out array for infrared microbolometers

Infrared imaging detectors require highly temperature sensitive sensors placed in a focal plane array. Due to the nature of these sensors, they can not simply be biased continuously, as this causes unwanted self heating that distorts the desired measurement. This is typically overcome by the use of pulse based biasing systems to reduce the time during which a sensor can measure incoming radiation, but this in turn requires a careful timing analysis and synchronisation in the design. This paper presents parts of the simulation design of a fully-integrated CMOS time-division analogue multiplexer circuit serving both as a biasing and a read-out circuit for a 16 times 16 array of uncooled microbolometers. The contribution and emphasis lies in the design of a control logic driver for a multiplexer based read-out circuit that not only ensures synchronous operation, but in doing so, also ensures that the sensors are biased for as short a period as possible. The initial design was completed for fabrication in a standard 0.35 mum CMOS process. Simulation results indicate a fully synchronous system, and the specific architecture implemented has reduced the biasing time of each element to less than 0.2% of the read-out time for an entire frame.