Spin hall-based analog to digital encoder for ultra-compact sensor nodes
Low-power and compact analog-to-digital converter (ADC) is essential for sensor nodes as a link between the sensor and data processing. In restricted-area and high-speed sensors such as image sensors, each pixel needs a compact ADC for parallel data conversion. CMOS implementations of such ADCs have faced three challenges: 1) the difficulty of integrating ADCs with sensors in every pixel due to the large area of analog circuits exacerbated by poor scaling of analog circuits in CMOS, 2) the high static power of analog data converters, 3) limited resolution of CMOS ADC directly related to the process variations. Enormous effort has been devoted to addressing the challenges in such ADCs. Different types of ADCs from single-slope to delta-sigma have been investigated to achieve this, however, they are still far from the required area, resolution and power-density of the sensors. SHADE proposes a novel breakthrough approach benefiting from the small footprint of spintronics into the current ADC architectures. This has solutions for both voltage- and time-mode ADCs. SHADE will lead to at least three orders of magnitude smaller area in comparison with the state-of-the-art ADCs. The voltage-mode approach eliminates the memory array interfacing between the ADC and processor leading to a significant power-saving. SHADE is a major step towards filling the huge gap between the area of ADCs and the available pitch of pixels. The main objectives of this project are to characterize and model the behavior of the magnetic element containing both switching and oscillation features, design and simulation of both voltage- and time-mode quantizers through a developed model, adapting the quantizer with different types of ADCs usually used in sensors and fabrication and testing of ADCs. My experience in device modeling, integrated circuit design and spintronics together with expertise in the host and the secondment have put me in a unique position to run such a promising project.