| 摘要 |
PURPOSE:To attain the A/D conversion with a simple circuit and by the integration of just one time without producing any error of the offset voltage of a comparator, by comparing the differentials between the time during which the integration output reaches the comparison voltage and the time during which the integration output reaches the voltage corresponding to the input voltage to calculate the value of the input voltage. CONSTITUTION:The voltage V1/2 is applied to the input terminal of a comparator 10 by a switching circuit 17; while the potential (V1+ VIN)/2 is applied to the input terminal of a comparator 11 (VIN: input voltage to be compared). The time counting is carried out until a coincidence signal is obtained to obtain a time T1' through the comparator. At the same time, a switch is connected to a terminal 15 and the potential V1 is applied to the input terminal of the comparator 10. Then the time counting is carried out until a coincidence signal is delivered to obtain a time T2' is obtained. At the same time, the time counting is carried out until a coincidence signal is delivered to obtain a time T3' at the comparator 11. These times T1'-T3' contain the error components Td produced by the offset voltage of the comparator. Then the real values T1-T3 are obtained with Td=0V and therefore the voltage VIN is equal to V1(T3'- T1')/(T2'-T1'). Thus it is possible to obtain the accurate VIN which contains no error due to the offset voltage of the comparator. |
