The LTC1773EMS is a current mode synchronous buck regulator controller that drives external complementary power MOSFETs using a fixed frequency architecture. The operating supply range is from 2.65V to 8.5V, making it suitable for 1- or 2-cell lithium-ion battery powered applications. Burst Mode® operation provides high efficiency at low load currents. 100% duty cycle provides low dropout operation which extends operating time in battery-operated systems.
The operating frequency is internally set at 550kHz, allowing the use of small surface mount inductors. For switching-noise sensitive applications, it can be synchronized up to 750kHz. Peak current limit is user programmable with an external high side sense resistor. A SYNC/FCB control pin guarantees regulation of secondary windings regardless of load on the main output by forcing continuous operation. Burst Mode operation is inhibited during synchronization or when the SYNC/FCB pin is pulled low to reduce noise and RF interference. Soft-start is provided by an external capacitor.
Synchronous rectification increases efficiency and eliminates the need for a Schottky diode, saving components and board space. The LTC1773EMS comes in a 10-lead MSOP package.
Feature
- High Efficiency: Up to 95%
- Constant Frequency 550kHz Operation
- VIN from 2.65V to 8.5V
- VOUT from 0.8V to VIN
- OPTI-LOOP® Compensation Minimizes COUT
- Synchronizable up to 750kHz
- Selectable Burst Mode Operation
- Low Quiescent Current: 80µA
- Low Dropout Operation: 100% Duty Cycle
- Secondary Winding Regulation
- Soft-Start
- Current Mode Operation for Excellent Line and Load Transient Response
- Low Quiescent Current: 80µA
- Low Shutdown IQ = 10µA
- ±1.5% Reference Accuracy
- Precision 2.5V Undervoltage Lockout
- Available in 10-Lead MSOP
Applications
- Cellular Telephones
- RF PA Supply
- Portable Instruments
- Wireless MODEMS
- Distributed Power Systems
- Notebook and Palm Top Computers, PDAs
- Single and Dual Cell Lithium-Ion Powered Devices
(Picture: Pinout)
