| 摘要 |
PURPOSE:To obtain an A-D converter with a small input current by connecting other terminal of 1st-4th analog switches to an analog input terminal, 1st and 2nd switch trees and a ground potential respectively. CONSTITUTION:A charge balanced analog-digital converter is provided. The other terminal of the 1st analog switch 12a is connected to the analog input terminal 16, the other terminal of the 2nd analog switch 32a is connected to the 1st switch tree 29 and the other terminal of the 3rd analog switch 12b is connected to the 2nd switch tree 30 and the other terminal of the 4th analog switch 32b is connected to the ground potential respectively. Thus, the analog input terminal 16 is subject to charge/ discharge with any voltage being 1/4 division of a reference voltage selected by a high-order 2-bit. Thus, the circuit using a small input current is obtained.
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