| 摘要 |
PURPOSE: A back-bias voltage detector is provided to ensure a stable operation by controlling a pumping action of a charge pump and limiting a level variance of a back bias voltage before and after generating a cell plate voltage. CONSTITUTION: A driver(201) provides a voltage(VCC) to a node(NODE) if an enable signal(EN is activated to a low level. A ring oscillator(203) generates an oscillation pulse while a potential of the node(NODE) is at a high level. A charge pump(202) drops the potential of the node(NODE) to a low level, and stops an operation of the ring oscillator(203). A voltage level varying part(204) determines that resistors(R2,R3) of th charge pump(202) are at a short state or not by a power-up inverting signal(PWRUPb) according to a generation time point of a cell plate voltage(VCP), and restricts a level variance of a back bias- voltage(VBB).
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