A calibration circuit for calibrating an adjustable capacitance of a circuit having a time constant depending on the adjustable capacitance, the calibration circuit generating a calibration signal for calibrating the capacitance and including a calibration loop, suitable to carry out a calibration cycle in several sequential steps. The calibration circuit includes a controllable capacitance for receiving a control signal and including an array of switched capacitors selectively activated by the control signal to connect to a first common node that conducts a voltage value depending on the total capacitance value of the activated capacitors; an assessment unit for comparing this voltage value with a reference voltage to output a logic signal that can transition between first and second logic levels; a control and timing unit to receive the logic signal and change the control signal to carry out a subsequent calibration step that is provided at the end of the integration interval during a comparison interval of a preset duration, which allows a transition of the logic signal to occur prior to the beginning of the consecutive calibration step.