RING OSCILLATOR CIRCUIT

A ring oscillator (50) comprises a chain of inverters (52) coupled between an oscillator supply node (54) and a reference node (56), and a current generator (58) coupled between the oscillator supply node and a system supply node (60) and configured to inject a current (IOSC) into the oscillator supply node. Each inverter comprises a first (NF) and a second (NL) low-side transistors coupled in series between the reference node and an output node of the inverter, and a first high-side transistor (PF1) coupled between the oscillator supply node and the output node of the inverter. The first low-side transistor and the first high-side transistor have respective control terminals coupled to an input node of the inverter to receive a respective inverter control signal (CK). The second low-side transistor has a control terminal coupled to the oscillator supply node. The ring oscillator circuit further comprises a biasing circuit (500) including a first bias transistor (NFZ) and a second bias transistor (NLZ) coupled in series between the reference node and the oscillator supply node. The first bias transistor has a control terminal configured to receive an oscillator control signal (StartP) indicative of whether the ring oscillator is in an active or inactive operation state. The second bias transistor has a control terminal coupled to the oscillator supply node. The first bias transistor is configured to selectively couple the reference node and the oscillator supply node in response to the ring oscillator being in an inactive operation state.