Affiliation:
1. School of Electronic Information Engineering, Tianjin University, Weijin Road, No.92, Nankai District, Tianjin 300072, China
Abstract
In this paper, a CMOS digital pixel sensor (DPS) with pixel-level ADC based on pulse width modulation (PWM) scheme is proposed to overcome the restriction of low supply voltage imposed by device scaling trend. The pixel operates with a dynamic current comparison scheme to avoid using complex in-pixel comparator and achieve a high dynamic range (DR). By adjusting clock frequency for different illumination, DR is further extended due to increasing the maximum detectable photocurrent and lowering the minimum detectable photocurrent. The pixel contains a photodiode (PD), an 11-bit in-pixel SRAM and other 11 transistors, and occupies an area of 7 μm × 7 μm, with a fill factor of 31.3% using a standard 65 nm CMOS technology. Simulation results show that this pixel can work at a supply voltage as low as 0.5 V with 120 dB DR and 80 dB linear DR (LDR). The properties of high DR and logarithmic response make the proposed digital pixel be capable of human eye. Frame rate achieves 246 fps with 640 × 480 pixel array by using in-pixel ADC and SRAM. This makes the digital pixel very suitable for high-speed snap shot digital camera application.
Publisher
World Scientific Pub Co Pte Lt
Subject
Electrical and Electronic Engineering,Hardware and Architecture,Electrical and Electronic Engineering,Hardware and Architecture
Cited by
2 articles.
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