Voltage detector, method for setting reference voltage and computer readable medium

A method for setting a reference voltage, the method to be used for setting a reference voltage generator including:

• a first write MOS transistor including a control gate and a floating gate;
• a second write MOS transistor connected in series with the first write MOS transistor, the second write MOS transistor including a control gate and a floating gate;
• a first output MOS transistor including a control gate and a floating gate that are electrically connected to the control gate and the floating gate of the first write MOS transistor;
• and
• a second output MOS transistor connected in series with the first output MOS transistor, the second output MOS transistor including a control gate and a floating gate that are electrically connected to the control gate and the floating gate of the second write MOS transistor,
• the first write MOS transistor and the second write MOS transistor are non-volatile storage elements each including a tunnel oxide film that allows electric charges to tunnel therethrough to be injected into the floating gate, and
• the first output MOS transistor and the second output MOS transistor are non-volatile storage elements each not including the tunnel oxide film and a reference voltage is output from a connection point between the first output MOS transistor and the second output MOS transistor, wherein
• electric charges stored in the floating gates of the first write MOS transistor and the first output MOS transistor are set in a reference state in which no currents flow from the first output MOS transistor into the second output MOS transistor,
• the second write MOS transistor and the second output MOS transistor enter an enhancement state in response to controlling the state of the electric charges stored in the floating gate through the tunnel oxide film of the second write MOS transistor, and
• the first write MOS transistor and the first output MOS transistor enter a depletion state in response to controlling the state of the electric charges stored in the floating gate through the tunnel oxide film of the first write MOS transistor.

A voltage detector for detecting whether an input voltage is no lower than a predetermined threshold voltage, the voltage detector comprising:

• a reference voltage generator configured to generate a reference voltage corresponding to the threshold voltage;
• a voltage selector configured to select one of the reference voltage and a setting voltage used to measure the reference voltage to be generated by the reference voltage generator and outputs the selected voltage;
• and
• a comparator including a CMOS inverter, the comparator configured to receive, at an input terminal of the CMOS inverter, one of the setting voltage and the reference voltage selected by the voltage selector and to receive the input voltage at a power supply terminal of the CMOS inverter, wherein
• the voltage selector selects the setting voltage when the voltage detector operates in a reference voltage detection mode in which the voltage detector detects the reference voltage that is to be generated by the reference voltage generator for the threshold voltage, and selects the reference voltage when the voltage detector operates in an actual operation mode in which the voltage detector detects whether the input voltage is no lower than the threshold voltage.