Ring oscillator including chain of plural series-connected comparators

Abstract

A ring oscillator generates a pulse signal having a frequency determined in response to a level change in the source voltage. For this, the ring oscillator comprises a voltage level detector for detecting an external source voltage and generating a reference voltage having a different level according to a voltage level of the clock signal, a chain unit for including a plurality of comparators which are connected in series and make a ring structure, each comparator comparing the reference voltage with an output signal of a preceding comparator in the ring structure under the control of the clock signal to thereby output an inverted signal, an output buffering unit for buffering the output signal of the chain unit and outputting the buffered signal, and an internal voltage providing unit for precharging the output terminal of the chain unit with an internal source voltage in a standby mode under the control of the clock signal, wherein the internal source voltage is being generated by voltage-dropping the external source voltage. By constructing the ring oscillator as above, the ring oscillator can minimize current consumption therein and more rapidly change the frequency of the pulse signal according to the level change of the source voltage.