| 摘要 |
PURPOSE:To prevent influence by switching noise by driving a digital circuit part by a synchronization signal from outside and driving a potential-voltage converter only while the digital circuit part is not driven. CONSTITUTION:An output of a potential outputting type detector 1 is input to a potential-voltage converter 2, and the output is led to a voltage comparator 3. Reference voltage Vref for discriminating from noise is set in the comparator 3, and when the output from the converter 2 exceeds this level, a logic level pulse signal is output to be introduced to a counter 4 to be counted. A synchronization clock phi is inputted from outside into the converter 2, the comparator 3 and the counter 4, by which operation of each of these circuits is regulated. That is, while the converter 2 performs conversion and holding operations, the comparator 3 and the counter 4 being a digital circuit part do not operate. Therefore during conversion and holding operations, a signal to cause noise is not generated from the digital circuit part.
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