| 摘要 |
PURPOSE:To attain A/D conversion with high accuracy at a low clock frequency by switching simultaneously a constant current source and a counter respectively in a converter utilizing a ramp integrating system so as to separate a required bit into plural number and counting them. CONSTITUTION:In giving a sampling instruction from a timing control circuit 9 to a sample holding circuit 2, an analog signal from an input terminal 1 is sampled, and a signal turning on a reset switch 5 and turning off switches 7a, 7b is outputted at the same time so as to reset an output of an integration circuit 30 to zero. When the sampling instruction is lost after a prescribed time, the switch 5 is turned off and the switch 7a is turned on and the integration circuit 30 starts integration from a constant current source 6a, then an output of a subtractor 13 is decreased with a prescribed slope. When the output reaches a reference voltage, an output of a comparator 16 is inverted, the switch 7a is turned off and the switch 7b is turned on so as to change the slope of the output of the subtractor 13. |
