| 摘要 |
PROBLEM TO BE SOLVED: To obtain sure diagnosis results and obtain diagnosis signals as simple DC outputs with diagnosis signals larger than a power supply voltage of an oscillator. SOLUTION: This diagnosis circuit 10-1 of the acceleration sensor supplies pulse signals for diagnosis to electrodes 23 and 25 of the acceleration sensor. The diagnosis circuit has an oscillator 15-1 for generating a reference clock signal eO upon receipt of the first power supply voltage V1, a phase inversion circuit 16 for generating tow-phase clock signalsϕ1 andϕ2 having phases different by 180 deg. from each other, when receiving the reference clock signal eO, and a comparison modulation circuit 17. The comparison modulation circuit 17 receives a second power supply voltage V2 larger than the first power supply voltage V1, which is comparing of a pair of comparators 19 and 21 for respectively comprising a reference voltage signal Vref, which is stepped down from the second power supply voltage V2 with the two-phase clock signals. Signals as modulated two-phase clock signalsϕ1 andϕ2 are supplied to the electrodes 23 and 25 of the acceleration sensor, enabling the acceleration sensor to carry out a self-testing diagnosis.
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