| 摘要 |
PURPOSE:To realize low power consumption and to make it possible to operate for a long time by using a sampling clock generated in a clock control circuit as a clock for operating an A/D converter and an address counter circuit. CONSTITUTION:An A/D converter circuit 30 receives the sampling clock generated in a clock control circuit 46 and performs the A/D conversion of a received echo signal at that timing. The circuit 40 outputs the digital sampling data as the sampling data signal. An address counter circuit 48 receives the sampling clock and starts the counting from a specified value. Therefore, when the sampling clock is not received, the charging and discharging by the sampling operation and the switching operation for conversion are not performed. In this case, only the standby current is consumed, and the current consumption is small. |
