In order for the IC to charge a battery, the power source at VBUS must be larger than the undervoltage lockout threshold of 3.3 V typical and the battery voltage, V(BAT) plus 200 mV typical to prevent SLEEP mode but less than the OVP threshold of 7.5 V typical. The input power source can be a low impedance USB port or wall adapter or a high impedance solar panel if the VBUS_DPM feature if appropriately configured.