2-Cell, Multi-Output DC/DC Converter with USB Power Manager

The LTC3456 is a complete power management system IC optimized for a variety of portable applications. The device generates two separate power rails: a 3.3V (fixed) Main supply and a 1.8V (adjustable) Core supply. In addition, the LTC3456 contains a USB power manager, a Hot Swap output, a low-battery indicator and an alwaysalive VMAX output. The LTC3456 takes power from one of three sources: a Wall adapter, a USB port or a 2-cell Alkaline/NiCd/NiMH battery, in that order of priority. Current drawn from the USB port is accurately limited to 100mA or 500mA based on the state of the USBHP pin.

The Main and Core switchers are all high efficiency, 1MHz fixed frequency PWM converters. Availability in a small (4mm × 4mm × 0.75mm) 24-pin QFN package makes the LTC3456 ideal for space-sensitive portable devices.

Applications

* GPS Portable Navigators

* MP3 Players

* Digital Cameras

* Handheld Computers

* Seamless Transition Between 2-Cell Battery, USB and AC Wall Adapter Input Power Sources

* Main Output: Fixed 3.3V Output

* Core Output: Adjustable from 0.8V to VBATT(MIN)

* Hot Swap™ Output for Memory Cards

* All Outputs Discharged to Ground During Shutdown

* Power Supply Sequencing: Main and Hot Swap Outputs Come Up After Core Output

* Accurate USB Current Limiting

* High Frequency Operation: 1MHz

* High Efficiency: Up to 92%

* Small (4mm × 4mm × 0.75mm) 24-Pin QFN Package