Smart card for performing biometric authentication and method of operating the same

A method of operating a smart card, the method comprising:

• measuring a first clock frequency of an external clock signal;
• selecting a first range from a plurality of first clock ranges based on the first clock frequency;
• outputting a sensor clock signal having a second clock frequency corresponding to the first range;
• and
• outputting sensing data for biometric authentication based on the sensor clock signal and first compensation image data,
• wherein the outputting of the sensor clock signal includes:
• determining a first reference frequency corresponding to the first range;
• and
• determining a first operation value for the second clock frequency by multiplying the first reference frequency by one of a negative power of 2 and a positive power of 2 based on the first reference frequency and a sensor clock range indicating an allowable frequency range of the sensor clock signal.

A smart card comprising:

• a frequency measurement circuit configured to measure a first clock frequency which an external clock signal has;
• a sensor clock output circuit configured to determine a first reference frequency corresponding to a first range being a clock range including the first clock frequency from among the plurality of first clock ranges, to determine a value for a second clock frequency by multiplying the first reference frequency by a power of 2 as, and to output a sensor clock signal having the second clock frequency;
• and
• a sensor circuit configured to select a second range from a plurality of second clock ranges based on the second clock frequency, to determine first compensation image data corresponding to the second range from among a plurality of compensation image data, and to generate final fingerprint image data as sensing data based on raw fingerprint image data and the first compensation image data.