IEEE Distinguished Talk, Prof Khaled N. Salama, KAUST
Title: Energy-Efficient Capacitance-to-Digital Converters for Low-Energy Sensor Nodes
Date: 2 Feb 2017
Speaker: Prof Khaled N. Salama
Energy efficiency is a key requirement for wireless sensor nodes, biomedical implants, and wearable devices. The energy consumption of the sensor node needs to be minimized to avoid battery replacement, or even better, to enable the device to survive on energy harvested from the ambient. Capacitive sensors do not consume static power; thus, they are attractive from an energy efficiency perspective. In addition, they can be employed in a wide range of sensing applications, such as pressure, humidity, biological, and chemical sensing. However, the capacitive sensor readout circuit—i.e., the capacitance-to-digital converter (CDC)—can be the dominant source of energy consumption in the system. Thus, the development of energy-efficient CDC architectures is crucial to minimizing the energy consumption of capacitive sensor nodes. In the first part of this talk, we propose several energy-efficient CDC architectures for low-energy sensor nodes. In the second part, we study the matching properties of small integrated capacitors, which are an integral component of energy-efficient CDCs. Despite conventional wisdom, we experimentally illustrate that the mismatch of small capacitors can be directly measured, and we report experimental mismatch measurements for sub-femtofarad integrated capacitors. We also correct the common misconception that lateral capacitors match better than vertical capacitors, and we identify the conditions that make one implementation preferable.