A CMOS photosensor test-chip for smoke detection applications

We report on a CMOS integrated photosensor specially tailored for smoke detection applications. A test chip consisting of an integrated photodiode, which reveals the light scattered by smoke particles, and of the related read-out electronics, has been designed and fabricated in 0.8 μm CMOS technology. The circuit design is based on the Switched Capacitor (SC) technique, and accomplishes low noise specifications by means of an accurate design of the first read-out stage and by employing Correlated Double Sampling (CDS) filtering blocks. Circuit simulations and preliminary results from the electrical characterization of the first chip prototype allowed the basic design methodology to be validated.