METHOD AND APPARATUS FOR ANALOG-TO-DIGITAL CONVERSION

摘要

One analog signal is selected out of a plurality of analog signals by a multiplexer and a capacitor is electrically charged through such a switch as adapted to be closed/opened by a start signal, and thereafter the capacitor is caused to discharge with a constant current with the switch opened. A level discriminating signal is led out when a voltage of the capacitor discharging goes below a predetermined discriminating level after the switch is opened. A stop signal is generated as a result of a logical operation of the analog signal and the level discriminating signal by an AND gate. A processing circuit accepts the stop signal and calculates a digital value corresponding to a time period from the time that the switch is opened to the time that the level discriminating signal is generated, and then moves to a subsequent processing operation.