Low Power Mixed Signal Sensor Design Techniques and Applications

As personal electronic devices have become ubiquitous in our society we increasingly depend on them to enhance our lives. Consumers continue to demand increased functionality, prolonged battery-life and improved dependability. The reliability and energy usage of analog sensors and their support circuitry is an area ripe for improvement, challenging Mixed Signal and Integrated Circuit (IC) designers to develop more robust and lower power sensors. This body of work focuses on advancements in several types of sensors and an associated circuit.;The first focus is on the required level conversion between sub-threshold low power sensors and nominal voltage circuits. Traditionally, analog sensors are some of the most power hungry devices. This work presents a new topology of level converter. It discusses two fabricated level converters in different technologies that are capable of reliably up-converting digital inputs of 190 mV to a nominal supply value.;The second section of this work presents an ultra-low power temperature sensor for implantation in mice. Temperature is essential to monitor because it is an indicator of a change in condition and its automation would improve researchers' ability to promptly identify changes. The sensor presented uses 5.84 nJ per sample of energy at 27°C with a 400 mV supply and it evaluates temperature between 10°C and 50°C.;The final sensor evaluates the reliability of digital circuits by focusing on detecting Bias Temperature Instability (BTI) and Hot Carrier Injection (HCI) to alert the user of a potential failure. A novel change to two cross-coupled inverters allows the circuit to act as a current comparator to detect degradations. The presented BTI sensor is capable of detecting threshold shifts with an error of 1.2 mV and is highly embeddable using only 13.7x times a standard inverter size.;All of these sensors and circuits are designed to help improve the interaction between users and on-chip sensing. They show significant improvements over existing designs in area, power, and sensitivity in each of the three applications. The methods presented in this work can easily be extrapolated to similar applications.