A mismatch compensated readout IC for an uncooled microbolometer infrared FPA

Abstract

In this paper, a low offset readout IC for an uncooled microbolometer infrared focal plane array is presented. It is shown that, due to the mismatch, the self-heating component of the IR-sensitive sensor’s current cannot be completely cancelled in the conventional differential structures. Therefore, there is large offset current which can desensitized the readout. The proposed readout is capable of achieving low-offset performance with using a feedforward path. A readout has been designed in a standard 0.18 μm CMOS technology. The post-layout simulation results show the feedforward path can attenuate the equivalent input offset current by about 14 dB at the presence of the 20% mismatch non-uniformity in the pixels. The noise equivalent temperature difference (NETD) is 48.5 mK which is increased by about 2.5 dB. Therefore, the overall dynamic range is increased 11.5 dB in the proposed readout. The readout draws 106.36 mA from a 3.3 V supply in a FPA with 352 × 288 pixels.