| 摘要 |
PURPOSE:To prevent occurrent of malfunction by detecting lowering of a boosting level formed in a bootstrap circuit, generating a pulse signal to form bootstrap voltage and using this for compensation of boosting level. CONSTITUTION:When the bootstrap circuit phix-B operates and a word line selection timing signal phix is raised, voltage level shifted by MOSFET Q10, Q11 becomes higher than logic threshold voltage of an inverter IV1, and accordingly, pulse phi becomes low level delaying by a delay time td. Consequently, precharge is made from a precharge MOSFET Q12 to a capacitor C. In this case, precharge is made to the capacitor C up to Vcc-Vth (threshold voltage of MOSFET Q12) and supplied to the gate of an MOSFET Q13. However, as a timing signal phix is in a high level higher than power source voltage Vcc, the MOSFET Q13 becomes off state. In an operation mode in which word line selection state lasts for a long time, if power source voltage lowers below Vcc, this is detected by an inverter IV1 and make it a high level. Thus, the word 11 line selection level can be compensated to above power source voltage Vcc. |
