| 摘要 |
In a over boosting prevention circuit that prevents over boosting of a voltage boosting circuit, ripples caused in the voltage boosting circuit are removed to prevent malfunctioning. The over boosting prevention circuit controls the output voltage Vout (<0V) of a charge pump circuit so that a difference (Vdd-Vout) between the power supply voltage Vdd and the output voltage Vout of the charge pump circuit does not exceed a predetermined value VMAX. That is, the charge pump circuit performs boosting operation when Vdd-Vout<VMAX, and stops the boosting operation when Vdd-Vout>VMAX. Influence of the ripples caused in the charge pump circuit is removed because the reference voltage Vref to an operational amplifier is determined relative to a ground voltage Vss.
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