A 140µA 34ppm/°C 30MHz Clock Oscillator in 28nm CMOS Bulk Process

This paper presents a 30MHz ring based clock oscillator in 28nm CMOS bulk process embedded in a negative feedback loop achieving 0.57% peak-to-peak temperature spread (worst case process corners) from - 40°C to 125°C and consuming 140μA current from 1.8V regulated voltage supply. Since the oscillation frequency of the ring oscillator is locked to Icomp/(C*Vref) by the loop, the bias current (Icomp) and voltage (Vref) can be independently temperature compensated to achieve very low temperature spread of the frequency in our implementation. The presented design achieves a temperature spread which is 10x lower than conventional RC oscillator in spite of high temperature coefficient (363 ppm/°C) of precision resistor available in the technology and absence of complementary temperature coefficient resistors. SPICE simulation results of the designed oscillator in 28nm CMOS bulk process along with performance summary and comparisons with other works have been included.