Impact analysis of deep-submicron CMOS technologies on the voltage and temperature independence of a time-domain sensor interface

This article presents a comparative study of a time-based sensor interface implemented in two standard CMOS technologies, 130 and 40 nm. The interface uses a ring oscillator to generate a pulse-width modulated signal of which the duty cycle is proportional to the sensor value. This results in a highly temperature- and supply voltage-independent output signal. Simulation results of both implementations are compared in terms of temperature and voltage dependence, power consumption and linearity. Also the noise propagation from the oscillator to the PWM output is discussed. Afterwards, the simulation results are compared to measured values of a 40-nm CMOS implementation. It is concluded that the interface topology is a robust solution for deep-submicron wireless sensor nodes in dynamic environments.