Patent ID: 7737663

Claim:
A charging and discharging control circuit for monitoring one of a voltage and a current of a secondary battery to control a connection between an external terminal and the secondary battery, comprising: an overcurrent detection circuit for monitoring a voltage at an overcurrent detection terminal to detect an overcurrent state; a control circuit for controlling the connection between the external terminal and the secondary battery based on an output from the overcurrent detection circuit; a pull-down circuit connected with the overcurrent detection terminal, for connecting the overcurrent detection terminal with a VSS terminal at a predetermined resistance value in the overcurrent state, the pull-down circuit comprising: a resistor; and a first N-channel transistor comprising a drain coupled to the overcurrent detection terminal and a source coupled to the resistor; a charger connection detection circuit connected with the overcurrent detection terminal, for detecting whether or not a charger is connected with the external terminal; and a switching circuit controlled in response to an output from the charger connection detection circuit, the switching circuit comprising a second N-channel transistor comprising a source coupled to the resistor of the pull-down circuit and a drain coupled to the VSS terminal, wherein the resistor is connected between the sources of the first and second N-channel transistors.