Using the LTC4078 standalone linear charger circuit you can design a very simple single-cell battery charger circuit for Li-Ion Li-Polymer battery .
This LTC4078 battery charger circuit works from both wall adapter and USB inputs. This charger can detect power at the inputs and automatically select the appropriate power source for charging.
A very simple Li-ion charger circuit can be designed using the EUP8054 integrated circuit which is a complete constant-current ,constant voltage linear charger for single cell lithium-ion batteries.
The EUP8054 Li-ion charger use few external components and can be used in many portable applications like mp3s , mobile phones , PDAs or other portable devices .
The charge voltage is fixed at 4.2V and the charge current can be programmed using an externally single resistor. The EUP8054 automatically terminates the charge cycle when the charge current drops to 1/10th .