A shared pair of input/output cells configured to be able to be connected to a first external resonator or a second external resonator. A first oscillator and a second oscillator are coupled to the shared pair input/output cells by a switching circuit. The switching circuit is configured to be able to connect either the first oscillator or the second oscillator to the pair of input/output cells.

A shared pair of input/output cells configured to be able to be connected to a first external resonator or a second external resonator. A first oscillator and a second oscillator are coupled to the shared pair input/output cells by a switching circuit. The switching circuit is configured to be able to connect either the first oscillator or the second oscillator to the pair of input/output cells.

A shared pair of input/output cells configured to be able to be connected to a first external resonator or a second external resonator. A first oscillator and a second oscillator are coupled to the shared pair input/output cells by a switching circuit. The switching circuit is configured to be able to connect either the first oscillator or the second oscillator to the pair of input/output cells.

The disclosure concerns an oscillator circuit (10) for a signal transmitter, the oscillator circuit (10) comprising: a resonant circuit (12) comprising a resonant inductor (LR) and a resonant capacitor (CR) parallel to the resonant inductor (LR) or comprising a crystal device, a driving branch (14) comprising a pump capacitor (CP) connected to the resonant circuit (12), a feedback branch (20) connected to the resonant circuit (12), a phase shifting circuit (22) connected to the resonant circuit (12) via the feedback branch (20), a comparator circuit (24) connected to the feedback branch (20) via the phase shifting circuit (22) and a driver circuit (28) connected to an output of the comparator circuit (24) and operable to charge the pump capacitor (CP).