| 摘要 |
<p>Provided is an A/D converter circuit wherein FSR is varied in accordance with a voltage variation range of analog signals regardless of how high or low the input levels are, thereby sufficiently enhancing the resolution of analog signals exhibiting small voltage variations. A successive approximation type A/D converter circuit comprises a comparator circuit (CMP) that determines whether an input analog voltage is higher or smaller than a comparison voltage; a register (SAR) that sequentially takes in determination results of the comparator circuit; and a local D/A converter circuit that converts a value of the register to a voltage, which is used as the comparison voltage. The successive approximation type A/D converter circuit further comprises a selecting means (SEL1) that selects one of a first group of voltages and supplies, to the local D/A converter circuit, the selected voltage as a first reference voltage that provides the upper limit value of a range of A/D convertible voltages; a selecting means (SEL2) that selects one of a second group of voltages having lower values and supplies, to the local D/A converter circuit, the selected voltage as a second reference voltage that provides the lower limit value of the range of A/D convertible voltages; and a register (REG1) that establishes a value that decides the selection states in the first and second selecting means.</p> |
