POWER LOSS (W) LTC3448 1.5MHz/2.25MHz, 600mA Synchronous Step-Down Regulator with LDO Mode FEATURES DESCRIPTIO High Efficiency: Up to 96% The LTC 3448 is a high efficiency, monolithic, synchronous Very Low Quiescent Supply Current: 32A During buck regulator using a constant frequency, current mode Linear Regulator Operation architecture. Supply current during operation is only 32A 600mA Output Current (Buck Converter) (linear regulator mode) and drops to <1A in shutdown. The Optionally Operates as Linear Regulator Below 2.5V to 5.5V input voltage range makes the LTC3448 ide- 3mAExternal or Automatic ON/OFF ally suited for single Li-Ion battery-powered applications. 2.5V to 5.5V Input Voltage Range 100% duty cycle provides low dropout operation, extend- 1.5MHz or 2.25MHz Constant Frequency Operation ing battery life in portable systems. At moderate output load or External Synchronization levels, PWM pulse skipping mode operation provides very No Schottky Diode Required low output ripple voltage for noise sensitive applications. Low Dropout Operation: 100% Duty Cycle The LTC3448 automatically switches into linear regulator 0.6V Reference Allows Low Output Voltages operation at very low load currents to maintain <5mV P-P Shutdown Mode Draws < 1A Supply Current output voltage ripple. Supply current in this mode is Current Mode Operation for Excellent Line and typically 32A. The switch to linear regulator mode occurs Load Transient Response at a threshold of 3mA. Linear regulator operation can be set Overtemperature Protected to on, off or automatic turn on/off. Low Profile (3mm 3mm) 8-Lead DFN and 8-Lead MSOP Packages Switching frequency is selectable at either 1.5MHz or U 2.25MHz, allowing the use of small surface mount induc- APPLICATIO S tors and capacitors. Cellular Telephones The internal synchronous switch increases efficiency and Personal Information Appliances eliminates the need for an external Schottky diode. Low Wireless and DSL Modems output voltages are easily supported with the 0.6V feed- Digital Still Cameras back reference voltage. The LTC3448 is available in a low MP3 Players profile 3mm 3mm DFN package or thermally enhanced Portable Instruments 8-lead MSOP. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131. Others pending. Efficiency and Power Loss vs Load Current TYPICAL APPLICATIO 100 1 V = 3.6V IN 90 V = 1.5V OUT 1.5V High Efficiency Regulator with Automatic LDO Mode T = 25C A 80 0.1 70 2.2H EFFICIENCY V V IN OUT 60 V SW IN 2.5V TO 5.5V 1.5V POWER LOSS RUN V C 50 0.01 C OUT IN OUT 4.7F 4.7F LTC3448 474k 40 22pF MODE 30 FREQ V FB 0.001 SYNC 20 316k GND 10 0 0.0001 3448 TA01a 0.0001 0.001 0.01 0.1 1 LOAD CURRENT (A) 23448 TA01b 3448f 1 EFFICIENCY (%) U ULTC3448 ABSOLUTE AXI U RATI GS (Note 1) V (LDO) Source Current .................................. 25mA Input Supply Voltage .................................. 0.3V to 6V OUT Peak SW Sink and Source Current ........................ 1.3A RUN, SYNC Voltages ................... 0.3V to (V + 0.3V) IN Operating Temperature Range (Note 2) .. 40C to 85C MODE Voltage ............................. 0.3V to (V + 0.3V) IN Junction Temperature (Notes 3, 7) ...................... 125C FREQ, V Voltages...................... 0.3V to (V + 0.3V) FB IN Storage Temperature Range ................ 65C to 125C SW Voltage .................................. 0.3V to (V + 0.3V) IN Lead Temperature (Soldering, 10 sec) V Voltage................................ 0.3V to (V + 0.3V) OUT IN MSOP Only ...................................................... 300C P-Channel Switch Source Current (DC) ............. 800mA N-Channel Switch Sink Current (DC) ................. 800mA UUW PACKAGE/ORDER I FOR ATIO ORDER PART ORDER PART TOP VIEW NUMBER NUMBER TOP VIEW V 1 8 RUN FB V 1 8 RUN FB LTC3448EDD LTC3448EMS8E V 2 7 SYNC OUT V 2 7 SYNC OUT 9 9 6 FREQ MODE 3 6 FREQ MODE 3 V 4 5 SW IN V SW 4 5 IN MS8E PACKAGE 8-LEAD PLASTIC MSOP DD PART MARKING MS8 PART MARKING DD PACKAGE T = 125C, = 40C/ W JMAX JA 8-LEAD (3mm 3mm) PLASTIC DFN EXPOSED PAD (PIN 9) IS GND LTBMK LBMJ T = 125C, = 43C/ W JMAX JA MUST BE SOLDERED TO PCB EXPOSED PAD (PIN 9) IS GND MUST BE SOLDERED TO PCB Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25C. V = 3.6V unless otherwise specified. A IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I Feedback Current 30 nA VFB V Regulated Feedback Voltage T = 25C 0.5880 0.6 0.6120 V FB A (Note 4) 0C T 85C 0.5865 0.6 0.6135 V A 40C T 85C 0.5850 0.6 0.6150 V A V Reference Voltage Line Regulation V = 2.5V to 5.5V (Note 4) 0.2 0.4 %/V FB IN V Output Overvoltage Lockout V = V V 15 35 55 mV OVL OVL OVL FB V = (V V ) 100/V 2.5 5.8 9.2 % OVL OVL OUT OUT V Output Voltage Line Regulation V = 2.5V to 5.5V (LDO) 0.1 0.8 %/V OUT IN I Peak Inductor Current V = 0.5V or V = 90%, 0.7 1 1.3 A PK FB OUT Duty Cycle < 35% V Output Voltage Load Regulation LDO, 1mA to 10mA 0.5 %/V LOADREG V Maximum Output Voltage (Note 9) V 0.7 V 0.3 V OUT(MAX) IN IN V Input Voltage Range 2.5 5.5 V IN 3448f 2 U WWW