Tutorial: Design of Physical-to-Digital Converters

Modern electronic systems employ increasing numbers of sensors to gather information about the physical world around us. This information, which is inherently non-electrical and analog in nature, needs to be digitized, often with increasingly demanding requirements on accuracy and power efficiency. This tutorial presents an integral approach to designing suitable physical-to-digital converters that goes beyond the conventional approach of combining a sensor, front-end circuit and ADC in terms of accuracy and efficiency. Approaches for embedding sensors into data-converter architectures are presented, including ratio-metric charge-balancing architectures and architectures that exploit feedback around the sensor. The need for suitable references and approaches for calibration and correction for cross-sensitivity are addressed. These concepts are illustrated using case studies of state-of-the-art temperature-to-digital, humidity-to-digital, flow-to-digital and light-intensity-to-digital converters.