A portable electronic device has a battery to provide power to operate the device, a connector including a power supply pin to be coupled to an external power supply, and a power manager having a battery charger circuit that draws power through the power supply pin to charge the battery. The power manager has a current limit feedback control loop that limits the drawn current in accordance with a predetermined output current rating of the external power supply. The power manager automatically changes the behavior of its control loop to stabilize operation of the coupled external power supply. Other embodiments are also described and claimed.