This paper introduces a novel sub-bandgap reference (sub-BGR) architecture that combines a single-BJT branch with a PTAT-embedded amplifier featuring an nMOS input stage. This sub-BGR design ensures temperature compensation and line regulation via a straightforward feedback loop, thereby eliminating the need for compensation capacitors, startup circuits, or trimming. Fabricated in a 55-nm CMOS technology, our sub-BGR demonstrates a temperature coefficient of 78.3ppm/◦C with a 0.9V supply, and maintains a line regulation of 0.153%/V across a voltage range of 0.9V to 1.2V, as evidence by measurements from ten chips. Additionally, it achieves a power supply rejection (PSR) ratio of -67dB at 10Hz, while supporting the addition of capacitive loads for further PSR enhancement. Notably, it occupies the smallest area (0.0144mm2) compared to similar sub-BGR designs.

Recently, miniature luminescence-based blood gas monitors have emerged as noninvasive, compact devices for continuous monitoring. Although these sensors demonstrate enhanced stability compared to traditional electrochemical-based sensors, they still face challenges such as photobleaching, temperature fluctuations, and material degradation, albeit at a reduced rate. This study introduces an algorithm aimed at compensating for drift in luminescence-based sensing. We implemented the algorithm on a custom evaluation board, incorporating an STM32WB35CC microcontroller and an ADPD4101 analog front end for luminescence lifetime sampling. The setup utilized a commercial platinum porphyrin-based luminescence sensor film. Experiments measured the partial pressure of oxygen in ambient air over three-day periods, comparing uncompensated measurements with those adjusted in real-time using the proposed compensation algorithm. The results indicated a ±0.3% change in luminescence lifetime over three days with the compensation method, in contrast to a drift of -2.6% to -3.6% without compensation. The proposed method enhances the long-term reliability and accuracy of luminescence-based oxygen sensing, with potential applications in extended home care and clinical monitoring.

Transcutaneous oxygen sensing is a noninvasive method for continuous monitoring of partial pressure of oxygen diffused through the skin that closely correlates with changes in arterial blood gases. A method for measuring transcutaneous oxygen, suitable for a wearable device, is luminescence oxygen sensing. This study aims to determine the optimum values of the system parameters for power, accuracy, and precision for the development of transcutaneous oxygen wearable based on a platinum-porphyrin film and the ADPD4101 analog front-end. For this purpose, we conducted several experiments using the CN0503 optical measurement system from Analog Devices, Inc. Based on the optimization experiments, we determined a 100 mA and 100 $\mu$s LED pulse intensity and width, and a 2 $\mu$s sampling period gave a good compromise between power and signal integrity. Using these settings, we observed a discernible $\tau$ response to changes in oxygen pressure from 0 to 418 mmHg.