Temperature and Supply Voltage Monitoring with Current-mode Relaxation Oscillators

This paper presents a new family of temperature and supply voltage sensors based on an improved current-mode relaxation oscillator. The proposed sensor circuit overcomes the finite input impedance of earlier current-mode relaxation oscillators, and it is paired with a novel opamp-free bandgap current reference. Two examples are presented: a V-DD-controlled oscillator, and a temperature-controlled oscillator. The temperature-controlled oscillator operates at 11.3 MHz and consumes 11.14 mu W while reaching a temperature nonlinearity error less than +0.85/-0.94 degrees C, a resolution figure of merit of 11.5 pJ.K-2, and an efficiency of 240 pJ/conv. The V-DD-controlled oscillator has a nonlinearity error less than +28.7/-30.0 mV from 1.2-1.8 V after two-point calibration.