On-Chip Excessive Heating Protection Scheme for Uncooled Micro-Bolometer Imagers

Joule heating effect of micro-bolometer sensors heats the elements rapidly during readout, and longtime heating might cause permanent damage of the detector. To solve this problem, we proposed a self-protection scheme based on an analog row select length of time detection circuitry. The protection circuit is effective for various sequential errors and improves the robustness of the whole detector. By implementing a cascaded OR-gate logic with trimmed edge delay, the row-level selection circuit layout is more regular with reduced area. To verify the proposed scheme, a 640$\times$512 array format uncooled infrared detector with 17$\mu$m pixel pitch is designed and fabricated in 0.18$\mu$m CMOS process. Power consumption of the circuits is below 50$\mu$W and the measured protection threshold of row period is around 360$\mu$s.