| 摘要 |
PURPOSE:To obtain a small-sized, fast A/D converter with small power consumption by using the same (n)-bit A/D converter twice repeatedly and thus obtaining a digital signal consisting of (n) high-order digit bits and (n) low-order digit bits. CONSTITUTION:An analog signal Vin inputted to an input terminal 20 is inputted to a sample holding circuit 21 and when a decision on the high-order digit bits is made, a reference voltage changeover switch 25 is placed at the side of the full-scale reference voltage VFS of a reference voltage generating circuit; and this is used as the reference voltage of the (n)-bit A/D converter 22 to convert the analog signal Vin from analog to digital, and thus the high-order (n)-bit signal is obtained and applied to a register 27 and a D/A converter 23. When a decision on the low-order digit bits is made, the reference voltage changeover switch 25 is placed at the side of the 1/2<n> full-scale reference voltage VFS/2<n> and the reference voltage is used as the reference voltage of the A/D converter 22; and the difference obtained by subtracting the output of the D/A converter 23 from the input analog signal Vin is A/D-converted to obtain the low-order (n)-bit signal. |
