An asynchronous analog self-powered CMOS sensor-data-logger with a 13.56 MHz RF programming interface

Design and implementation of a hybrid energy scavenging integrated circuit (IC) is presented which includes an asynchronous self-powered analog sensor-data-logger (SDL) unit and a 13.56 MHz radio-frequency (RF) programming interface. The SDL unit operates on an event-based analog self-powering technique where the energy for sensing, computation and non-volatile storage is harvested directly from the signal being sensed. By exploiting operational primitives inherent in a controlled hot-electron injection mechanism, the SDL unit eliminates the need for voltage regulation, energy storage, ADCs, MCUs and RAMs which are commonly used in traditional energy scavenging sensors. Remote programming and data interrogation of the SDL unit are performed using an integrated 13.56 MHz RF back-telemetry interface. The interface consists of a 6-instruction set digital command and control unit based on a token-ring architecture; a high-voltage generator for programming floating-gate (FG) transistors; and an RF front-end unit for communicating with an external reader. We show that the self-powered design is suitable for integration with electro-capacitive transducers (e.g., piezoelectric transducers) that can generate open-load voltages greater than 5 V and drive currents less than 200 nA. Measured results from prototypes fabricated in a 0.5-μ m standard CMOS process demonstrate that the IC consumes less than 90 nA in the self-powering mode and less than 200 μW of power in the RF-powering mode with an interrogation distance up to 40 mm. By combining self-powering and RF-powering, we show that the sensor experiences minimum down-time and can continuously monitor and record level-crossing statistics of different attributes of sensor signals.