Low-Power Always-on Camera (AoC) System with Workload Offloading to CMOS Image Sensor

In smartphones, an Always-on Camera (AoC) system to automatically unlock the display by face recognition. Due to the increase of the power consumption by continuous monitoring, the AoC system needs aggressive power saving policy such as clock and power gating. To apply efficient low-power schemes, an Application Processor (AP) must rapidly control the clock in sleep mode. A CMOS Image Sensor (CIS) needs: (1) to process workloads for the AP and (2) to inform the AP of all timings about various operations. In this paper, we propose a low-power SoC architecture for the AoC system with AP-centric clock control, 2-way communication between the AP and the CIS, and an algorithm offloading to CIS. Compared to the conventional, the power consumption can be reduced by approximately 80% in the idle mode of the CIS.