CMOS Analog-to-Digital Converter for Perovskite PV Sensing Applications Francis N. Mokogwu 1 , Arjuna Marzuki 2 , Annie Ng 1 , and Ikechi Ukaegbu 1, * 1 Department of Electrical and Computer Engineering, School of Engineering and Digital Sciences, Nazarba- yev University, Kabanbay Batyr Ave. 53, Astana, 010000, Kazakhstan; francis.mokogwu@nu.edu.kz 2 School of Science and Technology, Wawasan Open University, Penang, Malaysia; arjunam@wou.edu.my * Correspondence: annie.ng@nu.edu.kz (A.N.); ikechi.ukaegbu@nu.edu.kz (I.A.U.) Abstract: An 8-bit asynchronous single-ended Successive Approximation Register (SAR) Analog- to-Digital Converter (ADC) for the realization of a perovskite photovoltaic (PV) sensing application is presented. Various techniques have been proposed to enhance speed and power efficiency. A bootstrap transmission gate-based sample and hold circuit is proposed to improve sampling linear- ity and reduce power consumption. The sample and hold circuit is configured to operate at a 90% duty cycle, hence, giving it enough time for the conversion. A two-stage latch dynamic comparator is implemented to ensure high-speed and low power consumption. The SAR ADC also implements an asynchronous SAR logic block, controlled by an internal clock, which eliminates the need for an external clock. The proposed SAR ADC was designed in a UMC 180nm CMOS technology. The SAR ADC is tested with a sinusoidal analog input of 500 mV at 10 kHz frequency and a 4 MHz input clock frequency. The SAR ADC consumes a power of 2.67 mW at a supply of 1.5 V. The proposed ADC is an important unit for application in the fast growing perovskite-based PV industry. Keywords: perovskite PV; asynchronous SAR ADC; bootstrap sample and hold circuit, power effi- ciency 1. Introduction The global consonance in the development of renewable energy sources is a confir- mation of the infamous consequences of fossil fuel burning. The application of renewable energy increased by 3% in 2020 and was predicted to shoot up further by more than 8% reaching 8300TWh in 2021 [1]. Solar photovoltaic (PV) generation accounts for a large por- tion of this increase, placing it slightly behind wind energy harnessing and well above hydropower [2]. The IEA solar tracking report 2020 predicts that the global solar power usage will rise 15% from its present value to almost 3300TWh, thereby meeting the Sus- tainable Development Scenario (SDS) by 2030 [3, 4]. PV is also touted as the cheapest source of electric energy in the world. Crystalline Silicon-based PV cells and newer technologies such as perovskite PV cells have their ad- vantages and disadvantages. The perovskite PV trumps the crystalline Silicon-based PV in terms of flexibility, lightweight, semi-transparency, etc. Also, the ability of the perov- skite PV to function optimally under indoor or low light conditions makes it an ideal can- didate for certain applications such as microelectronic IoT nodes [5]. The PCE of single junction perovskites PV as reported by UNIST, South Korea is 25.7%, while the perov- skite/Si tandem (monolithic) cells developed by Oxford PV and HZB, Germany possess a record PCE of 32.5% [6, 7]. Despite the high PCE of the perovskite PV, its stability remains a critical issue. It degrades easily upon exposure to atmospheric conditions. The perovskite PV is fast becoming the preferred energy source for microelectronic devices. Also, building-integrated photovoltaics are becoming popular and perovskite PVs are integral to this application. Hence, it is crucial to monitor perovskite PV cells in integrated applications, detect degradation and report duly for replacement. To accu- rately detect degradation of perovskite PV cells in integrated applications, a mixed-signal sensing system architecture is designed. The requirements of such sensing system typi- cally include low power consumption, fast speed and high accuracy to enable real-time