| 摘要 |
PURPOSE:To improve the resolution of an A/D converter without considerably increasing the layout area of a series resistance type voltage divider of the A/D converter by adding resistor group, and a transistor to a power source side and a transistor, resistor group and a controller to a ground side. CONSTITUTION:An analog-to-digital converter 9 having a series resistance type voltage divider is prepared on a semiconductor substrate, and the voltage divider has (n) resistors of the same resistance value R connected in series, first selecting means for selecting the voltage divided values of the (n) series resistors, first resistor group of resistance value R/m connected in series with (m) resistors connected in series between the (n) series resistors and a power source, resistor group of resistance value R/m connected in series with (m) resistors connected in series between the (n) resistor group and a ground side, and a second selector for selecting to feed a current to any of (m) resistor group. The resistor group of R/4 of the power source side, a transistor, a transistor of ground side, resistor group of R/4, and a controller 10 are added. However, to raise the resolution to 1/64Vref of error, it is considered to increase the resistors R to increase the selector of D3-D1 side, thereby reducing the layout area.
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