Ultra low power RC oscillator for system wake-up using highly precise auto-calibration technique

An ultra low power RC oscillator for system wake-up is implemented using 0.18um CMOS process. The modern mobile systems need system clock which consumes low power and thus saves limited battery power in order to wake up from sleep-mode. A RC oscillator operates in the subthreshold region to reduce current consumption. The output frequency of RC oscillator is very weakly dependent on process and temperature variation using auto-calibration. This RC oscillator is featured as follows: the current consumption is 0.2 μA the supply voltage is 1.8V; the output frequency is 31.25 KHz with 1.52(Relative 3σ)% accuracy after calibration; it has only 0.4%/°C temperature coefficient; its size is 190 um } 80 um exclude bonding pad.