Warren Schroeder
Semtech

In any in-circuit rechargeable battery application, such as a mobile phone, Bluetooth headset or GPS receiver, power-management circuit designers have two options. They can either isolate the battery from the load while charging the battery, powering the load directly from the adapter, or they can keep the battery connected to the load, powering the load with the battery while charging the battery from the adapter. There are many commercial battery charger integrated circuits (ICs) that can implement both options. While both connection topologies have their own sets of tradeoffs, the advantages in cost and performance of the direct permanent connection of the load to the battery is the better choice in many applications. This paper explains how directly connecting a battery and load in a portable device can improve reliability and reduce cost with only a minor increase in charging time.