As portable products become more complex, the need for higher capacity batteries increases, with a corresponding need for more advanced battery chargers. Larger batteries require either higher charging current or additional time to charge to their full capacity. Most consumers look for shorter charge times, so increasing the charge current seems obviously preferable, but increasing charge current presents two major problems: first, with a linear charger, increased current creates additional power dissipation; secondly, the charger must limit the current drawn from the 5V USB bus to either 100mA or 500mA, depending on the mode that the host controller has negotiated.

This paper introduces Linear Technology’s LTC4088 High Efficiency Battery Charger, with the unique topology of a buck mode switching regulator working in tandem with a linear battery charger. Designed specifically for portable applications, the LTC4088 offers a dramatic advancement in battery charging and power path management technology, with its reduction in both heat generation and battery charge time.