A 70 MHz Temperature-Compensated On-Chip CMOS Relaxation Oscillator for Mobile Display Driver ICs

Abstract

A 70 MHz temperature-compensated onchip CMOS relaxation oscillator for mobile display driver ICs is proposed to reduce frequency variations. The proposed oscillator compensates for frequency variation with respect to temperature by adjusting the bias currents to control the change in delay of comparators with temperature. A bandgap reference (BGR) is used to stabilize the bias currents with respect to temperature and supply voltages. Additional temperature compensation for the generated frequency is achieved by optimizing the resistance in the BGR after measuring the output frequency. In addition, a trimming circuit is implemented to reduce frequency variation with respect to process. The proposed relaxation oscillator is fabricated using 45 nm CMOS technology and occupies an active area of 0.15 mm 2 . The measured frequency variations with respect to temperature and supply voltages are as follows: (i) ±0.23% for changes in temperature from -30 to 75°C, (ii) ±0.14% for changes in V DD1 from 2.2 to 2.8 V, and (iii) ±1.88% for changes in V DD2 from 1.05 to 1.15 V.