Analog-to-digital conversion circuit

摘要

The circuit includes a converter arrangement (1) which receives an analog input signal (FBAS) which contains a signal component with a predetermined frequency, and outputs a digital output signal (FBAS') with a clock signal (CLK) synchronised to the predetermined frequency. A device (2) combines at least two sample values of the output signal, and a low-pass filter (3) is supplied with a signal which is proportional to the two sample values. A frequency of an oscillator (4) is controlled by an output signal of the filter (3), and provides a signal from which the sampling clock of the analog-to-digital converter is derived. The input signal is pref. a video signal with a colour-burst, and the sample values are combined only during the period of the colour-burst. The sampling frequency is pref. four times the colour-burst frequency.