:arrow:AVR453: Smart Battery Reference Design (37 pages, revision C, updated 02/06)
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This application note describes the implementation of a smart battery using the Atmel ATmega406 microcontroller. The ATmega406 AVR microcontroller has been created with smart battery applications in mind. The feature set includes high accuracy ADCs, a TWI interface for SMBus communications, as well as independent hardware features that can protect the battery from incorrect use.
hi go to TI site they have very good Li-ion chargers with design examples BQ2000 series is there which proven.
Another solution is go to micrel site.They have Li-ion charger in very small package.Also Linear having same