ROIC for 3 um pitch detectors in portable applications

Abstract

Under the DARPA WIRED program, DRS advanced CQD film detectors, deposited by spin-coating from solution directly on readout integrated circuit (ROIC) wafers at room temperature. Such CQD fabrication can produce very small pixel pitch photodiode detectors, which need ROICs with proportionally small pixel pitch readout arrays fabricated on wafers in fully compatible CMOS process. CQD fabrication allows for very large format FPAs, limited only by the ROIC size. This paper presents CMOS ROIC detailed design ready for tapeout of a 3 μm pitch 1920 x 1080 fully optimized for low power and noise in battery powered portable applications. Although the ROIC was designed for CQD detector photodiodes, it could also be used with other 3 μm pitch IR detectors, such as the InGaAs type. Capacitive trans-impedance amplifier (CTIA) pixel was designed using ITAR-compliant 0.13 μm CMOS process. This particular 0.13 μm CMOS process was selected for CTIA pixel due to compact metal design rules for 3 μm pitch, high Gm, low FET noise and availability of high-density metal-insulator-metal (MIM) capacitor. The 3 μm pitch CTIA pixel has 22 Ke- well capacity and input-referred 37 e- or 48 e- readout noise, with and without correlated double sampling (CDS) respectively. The ROIC using 3 μm pitch 1920 x 1080 pixel array was designed to operate in ripple readout mode, both with and without the off-chip CDS. Pixels and single-slope 12 bit column A/D converter achieve < 1% non-linearity over 600 mV pixel output swing, with all necessary biases internally generated. Custom static random access memory (SRAM) is used for storing A/D conversion results with all timing clocks also internally generated. The data from the SRAM is serialized and readout through 4 x 600 Mbps LVDS serial outputs synchronized to 2 LVDS output clocks (2 data and 1 clock output on top and the bottom). The ROIC total power consumption was simulated at 536 mW from 1.2 V and 3.3 V power supplies. The FPAs using 3 μm pixel pitch ROIC and detector can be used in portable applications for atmospheric haze penetration, camouflage and NIR/SWIR designator detection. Such cost-effective targeting cameras can have around 10 hour operating time on single charge from 5000 mA-h, 3.8 V commercial Li-ion battery in portable applications.