Low-power relaxation oscillator and rfid tag using the same

An RFID tag comprising:

• a clock generation unit;
• and
• a digital unit supplying a clock control signal to control an output frequency of the clock generation unit,
• wherein the clock generation unit comprises:
• a constant current generation unit generating a current having a predetermined magnitude;
• a current varying unit controlling the current generated from the constant current generation unit according to a clock control signal to output the controlled current;
• a first controller and a second controller connected in parallel with output terminals of the current varying unit and passing or interrupting the current supplied from the current varying unit;
• a PMOS charging/discharging unit arranged between an output terminal of the first controller and an output terminal of the second controller;
• a first comparator and a second comparator connected to both ends of the PMOS charging/discharging unit, respectively, and each outputting a high or low level voltage upon receiving voltage charged in the PMOS charging/discharging unit;
• and
• a latch circuit delaying the voltages output from each of the first and second comparators to output oscillation signals.