DESCRIPTION
The LTC®3421 is a high efficiency, current mode, fixed frequency, step-up DC/DC converter with true output disconnect and inrush current limiting. The device includes a 0.10Ω N-channel MOSFET switch and a 0.14Ω P-channel synchronous rectifier. This product has the ability to simply program the output voltage, switching frequency, current limit, soft-start, Burst Mode threshold and loop compensation with external passive components.
Quiescent current is only 12µA during Burst Mode operation, maximizing battery life in portable applications. The oscillator frequency can be programmed up to 3MHz and can be synchronized to an external clock applied to the SYNC pin. An open-drain uncommitted low-battery comparator is included. The part maintains operation in applications with a secondary cell powering the output voltage during shutdown.
Other features include: 1µA shutdown, antiringing control, thermal limit and reference output.
The LTC3421 is available in a small 4mm × 4mm QFN package.

FEATURES
■ Synchronous Rectification: Up to 96% Efficiency
■ True Output Disconnect
■ Inrush Current Limiting
■ Very Low Quiescent Current: 12µA
■ Up to 1.5A Continuous Output Current
■ Fixed Frequency Operation Up to 3MHz
■ 0.5V to 4.5V Input Range
■ 2.4V to 5.25V Adjustable Output Voltage
■ Guaranteed 1V Start-Up
■ Programmable Current Limit
■ Programmable Soft-Start
■ Synchronizable Oscillator
■ Manual or Automatic Burst Mode® Operation
■ Low-Battery Comparator
■ <1µA Shutdown Current
■ 1.22V Reference Output Voltage
■ Small (4mm × 4mm) Thermally Enhanced QFN Package

APPLICATIONS
■ Handheld Computers
■ Cordless Phones
■ GPS Receivers
■ Battery Backup Supplies