A 1.4-V 28-μW CMOS OSCILLATOR AS A CAPACITIVE SENSOR INTERFACE

摘要

The aim of this work is to present a novel CMOS low-voltage (1.4V) low power (28 μW) oscillator, designed in a traditional CMOS 0.5μ process, to be used in integrated capacitive sensor interfaces. It makes use of an hysteresis comparator, which has been adapted to be used for low-voltage single supplies. The output frequency is inversely proportional to the capacitance. High linearity is achieved for capacitive values higher than 1 pF. The considered capacitive range is (10 fF, 100 pF), to which a frequency span of about (300 Hz, 3 MHz) corresponds. The power consumption at 1.4 V-supply is only 28 μW. The circuit shows low sensitivity to supply discharges (less than 0.03 %/mV) and good output linearity for temperature variations (in the range 0-80 °C). The sensor resolution (Δf/f) is about 0.05 %. These characteristics have been verified to be better than the corresponding performance of a typical solution presented in literature, which has been simulated in the same technology.