A charger integrated circuit for charging a battery device including a first battery and a second battery connected to each other in series. The charger integrated circuit includes a first charger to be connected to a connection node between the first and second batteries, a second charger to be connected between the input voltage terminal and a high voltage terminal of the battery device, and a balancing circuit to balance voltages of the first and second batteries. The first charger is to provide a first charge current to the connection node in a first charge mode. The second charger is to directly charge the battery device by providing a second charge current to the high voltage terminal in a second charge mode.