Disclosed is a circuit for converting an analog input signal into a digital code (b1-bN), comprising a delay circuit adapted to generate a periodical signal having a delay as a function of the analog input signal value; and a quantization stage for converting the delayed periodical signal into the digital code. The circuit converts an analog voltage or current into the time-domain, thus facilitating the implementation of high-speed analog-to-digital converters into submicron technologies, in particular CMOS technologies. A method of converting an analog input signal into a digital code (b1-bN) is also disclosed.