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This paper reports the development of a new dual-polarity Direct-Injection (DI) Readout Integrated Circuit (ROIC), called
MT6420DDA, designed to support back-to-back connected photodiodes with a single contact per pixel using dual pixel
input circuitries suitable for both p-on-n and n-on-p type detectors. The ROIC has a format of 640 × 512 (VGA) and a
pixel pitch of 20μm, and can be used to build dual-color or dual-band FPAs working in the MWIR and/or LWIR bands.
The ROIC supports snapshot operation with Integrate-then-Read (ITR) and Integrate-while-Read modes (IWR).
MT6420DDA has a system-on-chip architecture, with programmable biasing, timing, and configuration. The ROIC
supports 2, 4, and 8-output modes at pixel output rates up to 12.5 MHz per output. It runs on 3.3 V analog and 1.8 V
digital supplies, and dissipates less than 135 mW in the 4-output mode at 10 MHz. The ROIC has separate programmable
full well capacitance values of 1.5 Me-, 3.0 Me-, and 6.0 Me- for both polarities in the high-gain (HG), mid-gain (MG),
and low-gain (LG) modes. The ROIC supports two type of polarity switching modes as PSBF (Polarity Switching between
Frames) and PSWF (Polarity Switching within Frames). In the PSBF modes, an alternating input polarity is used for each
detector type for each frame during each integration period, possibly with different full-well and integration time settings.
In the PSWF mode, both type of pixels are exposed almost simultaneously, where detector current is integrated in a time
multiplexed manner using the two separate integration capacitors of the pixel input circuitry. The PSBF mode is simple,
but the time stamp for each image frame is different. The PSWF mode is complex, but results in a pseudo simultaneous
registration of images for each color or spectral band. The ROIC has been developed for cryogenic operation down to
65K with an input referred noise level of less than 470 e- rms in the low-gain (LG) mode at 77K. The MT6420DDA ROIC
has been fabricated on 200 mm wafers containing a total of 89 parts with typically 75 working parts. Mikro-Tasarim
provides tested ROIC wafers and offers compact test electronics and software for its ROIC customers to shorten their FPA
and camera development cycles. MT6420DDA can also be used together with MTAS1410X8, an 8-channel ASIC from
Mikro-Tasarim, that can be used to drive the FPA and digitize its analog outputs to build compact and low-noise
Integrated-Detector-Dewar-Cooler-Assembly (IDDCA) units and camera cores.
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