Patent ID: 7368931

Claim:
A mismatch test circuit for measuring a mismatch between a first input signal and a second input signal, the mismatch test circuit comprising: a sampling pulse oscillating unit for generating a sampling pulse enabled at constant period; and a similarity determining unit for determining a similarity between the first input signal and the second input signal at an enabling timing of the sampling pulse, wherein the similarity determining unit includes: a strobe analyzing unit for generating strobe signals including logic values given by sampling the first input signal at the enabling timing of the sampling pulse; and a mismatch determining unit for determining whether a logic value of the second input signal at a timing when the strobe signal is generated is identical to a logic value of a current strobe signal, wherein the sampling pulse includes N sampling pulse bits enabled at predetermined intervals according to an input of the first or second input signal, and the sampling pulse oscillating unit includes: N oscillators connected in cascade, for receiving transition of a previous oscillator and transiting an output, a transition delay time of the oscillator being controlled depending on the frequency control signal; and N drivers for driving outputs of the oscillators to output the sampling pulse bits.