Photovoltaic-Energy-Powered Temperature-Sensing Chip With Digital Output and Built-in Energy Harvesting Circuit

In this letter, a temperature-sensing chip with a built-in photovoltaic (PV) energy harvesting circuit is proposed. The temperature-sensing circuit includes a bipolar-junction-transistor (BJT)-based sensing circuit, a gain stage, and a successive approximation register (SAR) analog-to-digital converter (ADC), while the energy harvesting circuit is a boost dc–dc converter with a perturbation-and-observation maximum power point tracking circuit. The main goal of this work is successful chip integration. To the best of our knowledge, this is the first chip that integrates a temperature sensor, an ADC, an energy harvesting circuit, a clock generator, and other related circuits into a single chip. While conventional temperature-sensing chips are typically powered by a stable power supply voltage (which may not be available in Internet of Things devices), the proposed chip is powered by the built-in boost converter, whose output voltage inevitably has ripples. Despite this, the performance of our temperature-sensing chip is excellent. In addition, the built-in clock generator can generate signals with a subhertz frequency, which is difficult to achieve with low-power requirements. The chip was fabricated using the TSMC 0.18-μm 1P6M mixed-signal process. The measured results indicate that the sensed temperature of the proposed chip ranges from –20 °C to 80 °C with 0.17 °C resolution. The error is within ±0.8 °C, and R ² representing linearity reaches 0.99988.