LTC4098 Li-Ion Polymer battery charger
Using the LTC4098 USB Power-Path controller you can design an high efficiency , full-featured Li-Ion Polymer battery charger using few external electronic components . This Li-Ion Polymer battery charger circuit can be used with many power distribution sources like: USB, wall adapter, automotive, Firewire or other high voltage DC/DC converters, and a Li-Ion/Polymer battery.
For automotive and other high voltage applications, the LTC4098 interface with a Linear Technology external switching regulator to provide a high efficiency high voltage power path.
An overvoltage circuit protects the LTC4098 from high voltage damage on the USB/wall adaptor inputs with an N-channel FET and an resistor .
The voltage on the pin7 (Prog) pin always represents the actual charge current by using the following formula: IBAT =(VPROG/RPROG)x1030
The charge current is programmed using a single resistor from PROG to ground.The program resistor and the charge current are calculated using the
following equations :RPROG =1030V/ICHG ; ICHG =1030V/RPROG .
The charge voltage will be 4.2V with 0.5 accuracy .
As you can see in the schematic circuit this charger is very simple an you need to apply just few easy equations to design a high efficiency Li-Ion Polymer charger .