| 摘要 |
PURPOSE: A power-supply detection circuit of a flash EEPROM is provided to output a voltage for power-supply detection by using a condenser when an external power-supply is detected for a cell write operation in flash EEPROM or a power-supply is detected at a standby mode, and detects a power-supply by being synchronized to a voltage detection enable signal of a low frequency having a very short enable period. CONSTITUTION: A power-supply detection circuit of a flash EEPROM includes a voltage output part(21) for detecting a power-supply, voltage comparators(22A,22B), detection voltage output parts(23A,23B), enable signal generator(24), and a power-supply detection controller(25). In the voltage output part(21), a source and a drain are respectively connected to a power terminal(VDD) and a ground terminal(VSS), charge a voltage of a predetermined level from the power terminal(VDD) by using two pairs of condensers whose gates are connected in common, and generates the charged voltage as upper and lower power detection voltages(VR)(VBO). The voltage comparators(22A,22B) compare the voltages(VR,VBO) with reference voltages(Vref1,Vref2). Detection voltage generators(23A,23B) respectively output voltage signals(VDD_F)(VDD_S) generated from the voltage comparators(22A,22B). The enable signal generator(24) has a very short enable period as compared with a disable period, and has the same frequency as a standby clock signal. The power-supply detection controller(25) switches the voltage output part(21) and the voltage comparators(22A,22B) to an enable state by being synchronized to the voltage detection enable signal(VDET_EN).
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