DESCRIPTION
The LTC®3557/LTC3557-1 is a highly integrated power management and battery charger IC for single cell Li-Ion/Polymer battery applications. It includes a PowerPathTM manager with automatic load prioritization, a battery charger, an ideal diode and numerous internal protection features. Designed specifically for USB applications, the LTC3557/LTC3557-1 power manager automatically limits input current to a maximum of either 100mA or 500mA for USB applications or 1A for wall adapter powered applications.

FEATURES
■ Seamless Transition Between Input Power Sources:
   Li-Ion Battery, USB, 5V Wall Adapter or High
   Voltage Buck Regulator with Bat-TrackTM
■ 200mΩ Internal Ideal Diode Plus Optional External
   Ideal Diode Controller Provides Low Loss Power
   Path When Input Current is Limited or Unavailable
■ Triple Adjustable High Effi ciency Step-Down
   Switching Regulators (600mA, 400mA, 400mA IOUT)
■ Pin Selectable Burst Mode® Operation
■ Full Featured Li-Ion/Polymer Battery Charger
■ 1.5A Maximum Charge Current with Thermal Limiting
■ Battery Float Voltage:
   4.2V (LTC3557)
   4.1V (LTC3557-1)
■ Low Profi le 4mm × 4mm 28-Pin QFN Package

APPLICATIONS
■ HDD-Based MP3 Players
■ PDA, PMP, PND/GPS
■ USB-Based Handheld Products