A CMOS solar power to frequency converter with calibration circuits for monitoring sunlight intensity of crops

In this paper, a CMOS solar power to frequency converter with calibration circuits for monitoring sunlight intensity of crops is newly proposed. A calibration technique is proposed in this work. Another innovation is that the outputs of the proposed chip are directly digitized, they could be easily sent over a wide range of transmission media, such as PSN, radio, optical, IR, ultrasonic, and etc. Before performing the proposed calibration circuits, the maximum linear error is 15.11%. After calibration, the maximum linear error is reduced to 0.72%. Compared to each other, the linear error is enhanced almost 21 times. The solar power ranges from 37.86 to 380.67 W/m², and its corresponding output frequency range is 1.39 to 2.1 MHz. The chip area is 1.057 × 1.057 mm². The proposed chip is suitable for devices of measuring solar power, such as devices of monitoring sunlight intensity of crops.