The LTC3559/LTC3559-1 are USB battery chargers with dual high efficiency buck regulators. The parts are ideally suited to power single-cell Li-Ion/Polymer based handheld applications needing multiple supply rails.Battery charge current is programmed via the PROG pin and the HPWR pin, with capability up to 950mA at the BAT pin. The battery charger has an NTC input for temperature qualified charging. TheCHRGpin allows battery status to be monitored continuously during the charging process. An internal timer controls charger termination.Each monolithic synchronous buck regulator provides up to 400mA of output current while operating at efficiencies greater than 90% over the entire Li-Ion/Polymer range. A MODE pin provides the flexibility to place both buck regulators in a power saving Burst Mode operation or a low noise pulse skip mode.The LTC3559/LTC3559-1 are offered in a low profile thermally enhanced 16-lead (3mm × 3mm) QFN package.ApplicationsSD/Flash-Based MP3 PlayersLow Power Handheld Applications