The described analog-digital converter comprises quantization means having an input for receiving an analog quantity to be converted, a register having an output for providing a digital quantity corresponding to the analog quantity, a timing pulse generator and logic means connected to the quantization means, the register and the timing pulse generator and capable of responding to a conversion request signal by activating the quantization means in such a manner as to make them carry out predetermined operations timed by the timing pulses and load into the register the digital quantity to be provided at the output. With a view to permitting the converter to function even when a system clock is not available, the timing pulse generator, which is incorporated in the integrated circuit that comprises the rest of the converter, comprises an oscillator capable of being started/stopped by a binary signal applied to its activation input and the logic means are capable of generating a stop signal of the oscillator and comprise means for generating the binary signal to be applied to the activation input of the oscillator. This signal assumes a first or a second binary state corresponding, respectively, to activation and deactivation of the oscillator in response to, respectively, the conversion request signal and the stop signal of the oscillator.