| 摘要 |
PURPOSE:To reduce the chip area in an integrated circuit, by decreasing the number of voltage comparison circuits for an A/D conversion circuit of parallel comparison system. CONSTITUTION:Voltage comparison circuit 38-42 compare an analog signal input voltage e0 with voltage division voltages e1,e4,e7,e10 and e13, and a boundary detection circuit 45 detects boundary points of the circuit 38-42. Signal lines 58-62 of the circuit 45 drive switches 46-55 and become inputs to a decoder 63. The switches 46-55 are turned on or off in accordance with H, L of the driving signal for the lines 58-62 to give the voltage e2, and e3-e15 to either of a common output terminals 56 and 57. Thus, the outputs of comparison circuits 43, 44 attain three kinds of states in correspondence to the magnitude of the voltage inputted to each voltage comparator and switch means. Then, the decoder 63 outputs three kinds of digital signals to output terminals 64-67 depending on the three kinds of input states. Thus, since the number of voltage comparison circuits can remarkably be reduced in comparison with conventional systems, the chip area can be reduced. |
