Charge/discharge control circuit and battery device

A charge/discharge control circuit to be contained in a battery device including:

• a secondary cell;
• an external positive terminal and an external negative terminal to which a load, a positive pole of a charger, and a negative pole of the charger are connectable;
• a charge control FET configured to control charging of the secondary cell;
• and
• a discharge control FET configured to control discharging of the secondary cell,
• the charge/discharge control circuit comprising:
• a first power supply voltage input terminal to which, out of a first power supply voltage and a second power supply voltage, the first power supply voltage is supplied, the first power supply voltage and the second power supply voltage being generated by the secondary cell;
• a second power supply voltage input terminal to which the second power supply voltage lower than the first power supply voltage is supplied;
• a charge control terminal connected to a gate of the charge control FET;
• a discharge control terminal connected to a gate of the discharge control FET;
• a voltage detection terminal to which a voltage applied to the external positive terminal is supplied;
• an NMOS transistor configured to communicate the discharge control terminal and the voltage detection terminal;
• and
• a bipolar transistor having a collector connected to a drain of the NMOS transistor, an emitter connected to a source of the NMOS transistor, and a base connected to a bulk of the NMOS transistor and the second power supply voltage input terminal.