LTC1773 Synchronous Step-Down DC/DC Controller FEATURES DESCRIPTIO The LTC 1773 is a current mode synchronous buck regu- High Efficiency: Up to 95% lator controller that drives external complementary power Constant Frequency 550kHz Operation MOSFETs using a fixed frequency architecture. The oper- V from 2.65V to 8.5V IN ating supply range is from 2.65V to 8.5V, making it V from 0.8V to V OUT IN suitable for 1- or 2-cell lithium-ion battery powered appli- OPTI-LOOP Compensation Minimizes C OUT cations. Burst Mode operation provides high efficiency at Synchronizable up to 750kHz low load currents. 100% duty cycle provides low dropout Selectable Burst Mode Operation operation which extends operating time in battery-oper- Low Quiescent Current: 80A ated systems. Low Dropout Operation: 100% Duty Cycle Secondary Winding Regulation The operating frequency is internally set at 550kHz, allow- Soft-Start ing the use of small surface mount inductors. For switch- Current Mode Operation for Excellent Line and ing-noise sensitive applications, it can be synchronized up Load Transient Response to 750kHz. Peak current limit is user programmable with Low Shutdown I = 10A Q an external high side sense resistor. A SYNC/FCB control 1.5% Reference Accuracy pin guarantees regulation of secondary windings regard- Precision 2.5V Undervoltage Lockout less of load on the main output by forcing continuous Available in 10-Lead MSOP operation. Burst Mode operation is inhibited during syn- U chronization or when the SYNC/FCB pin is pulled low to APPLICATIO S reduce noise and RF interference. Soft-start is provided by an external capacitor. Cellular Telephones RF PA Supplies Synchronous rectification increases efficiency and elimi- Portable Instruments nates the need for a Schottky diode, saving components Wireless MODEMS and board space. The LTC1773 comes in a 10-lead MSOP Distributed Power Systems package. Notebook and Palm Top Computers, PDAs , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Single and Dual Cell Lithium-Ion Powered Devices OPTI-LOOP and Burst Mode are registered trademarks of Linear Technology Corporation. Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815. TYPICAL APPLICATIO V IN 2.65V TO 8.5V High Efficiency 100 + V = 3.3V 95 IN SYNC/FCB V R C IN SENSE IN 0.025 68F 90 V = 5V IN RUN/SS SENSE 85 L1 0.1F V = 8V IN I TG TH 3H 80 V LTC1773 OUT 47pF 30k 2.5V SW 75 220pF 70 V BG FB GND 65 + Si9801DY C OUT 60 180F L = SUMIDA CDRH6D28-3R0 80.6k 55 169k 1 10 100 1000 5000 1773 F01 OUTPUT CURRENT (mA) 1773 F1b Figure 1. Step-Down Converter 1773fb 1 EFFICIENCY (%) U ULTC1773 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART Input Supply Voltage .............................. 0.3V to 10.0V TOP VIEW NUMBER I Voltage ................................................ 0.3V to 2.5V TH I 1 10 SW TH RUN/SS, V SENSE Voltages .................. 0.3V to V FB, IN RUN/SS 2 9 SENSE LTC1773EMS SYNC/FCB 3 8 V IN SYNC/FCB Voltage ...................................... 0.3V to V IN V 4 7 TG FB GND 5 6 BG BG, TG Voltages...........................................0.3V to V IN MS PART MARKING MS PACKAGE SW Voltage ...................................................5V to 11V 10-LEAD PLASTIC MSOP Operating Ambient Temperature Range LTMV T = 125C, = 120C/W JMAX JA (Note 2) ...............................................40C to 85C Order Options Tape and Reel: Add TR Junction Temperature (Note 3)............................. 125C Lead Free: Add PBF Lead Free Tape and Reel: Add TRPBF Storage Temperature Range ..................65C to 150C Lead Free Part Marking: