EFFICIENCY (%) LTC3408 1.5MHz, 600mA Synchronous Step-Down Regulator with Bypass Transistor FEATURES DESCRIPTIO Dynamically Adjustable Output from 0.3V to 3.5V The LTC 3408 is a high efficiency monolithic synchro- 600mA Output Current nous buck regulator optimized for WCDMA power ampli- Internal 0.08 P-Channel MOSFET Bypass fier applications. The output voltage can be dynamically Transistor programmed from 0.3V to 3.5V. At V > 3.6V an internal OUT High Efficiency: Up to 96% 0.08 bypass P-channel MOSFET connects V directly OUT 1.5MHz Constant Frequency Operation to V , eliminating power loss through the inductor. IN No Schottky Diode Required The input voltage range is 2.5V to 5V making the LTC3408 Low Dropout Operation: 100% Duty Cycle ideally suited for single Li-Ion battery-powered applica- 2.5V to 5V Input Voltage Range tions. 100% duty cycle provides low dropout operation, Shutdown Mode Draws < 1A Supply Current extending battery life in portable systems. Current Mode Operation for Excellent Line and Load Transient Response Switching frequency is internally set at 1.5MHz, allowing Overtemperature Protected the use of small surface mount inductors and capacitors. Available in 8-Lead 3mm 3mm DFN Package The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. U The LTC3408 is available in a low profile (0.75mm) 8-lead APPLICATIO S 3mm 3mm DFN package. WCDMA Cell Phone Power Amplifiers , LTC and LT are registered trademarks of Linear Technology Corporation. Wireless Modems U.S. Patent Numbers: 5481178, 6580258, 6304066, 6127815, 6498466, 6611131 TYPICAL APPLICATIO Efficiency Power Lost vs Load Current WCDMA Transmitter Power Supply 100 1 90 4.7H* V V IN OUT 2.7V V SW 3 V IN REF 80 C ** TO 5V C OUT 600mA IN 4.7F 10F 70 LTC3408 0.1 CER CER 60 RUN V OUT 50 REF OUTPUT GND 40 WCDMA PROGRAMMING 0.01 RF PA 30 DAC V = 1.2V OUT 20 V = 1.5V *MURATA LQH32CN4R7M11 OUT 3403 TA01 V = 1.8V **TAIYO YUDEN JMK212BJ475MG OUT 10 V = 2.5V TAIYO YUDEN JMK212BJ106MN OUT 0.01 0 1 10 100 1000 LOAD CURRENT (mA) 3408 F04 3408f 1 POWER LOST (W) U ULTC3408 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) Input Supply Voltage (<300s) .................. 0.3V to 6V ORDER PART TOP VIEW Input Supply Voltage (DC) ....................... 0.3V to 5.5V NUMBER V 1 8 V RUN, REF, V Voltages .......................... 0.3V to V OUT OUT OUT IN LTC3408EDD V 2 7 V SW Voltage (DC) ......................... 0.3V to (V + 0.3V) IN IN IN 9 GND 3 6 REF P-Channel Switch Source Current (DC) ............. 800mA SW 4 5 RUN N-Channel Switch Sink Current (DC) ................. 800mA Peak SW Sink and Source Current ........................ 1.3A DD PACKAGE DD PART MARKING 8-LEAD (3mm 3mm) PLASTIC DFN Bypass P-Channel FET Source Current (DC).............. 1A EXPOSED PAD IS GND (PIN 9) MUST BE SOLDERED TO PCB LAEA Operating Temperature Range (Note 2) .. 40C to 85C T = 125C, = 43C/ W, = 3C/ W Junction Temperature (Note 3)............................ 125C JMAX JA JC Storage Temperature Range ................ 65C to 125C 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. A V = 3.6V unless otherwise specified. IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Regulated Output Voltage V = 1.1V 3.23 3.3 3.37 V OUT REF V = 0.1V 0.25 0.3 0.35 V REF V Output Voltage Line Regulation V = 2.5V to 5V, V = 0.6V 0.1 0.4 %/V OUT IN REF I Peak Inductor Current V = 3V, V = 0.9V 0.70 1 1.25 A PK IN REF V Output Voltage Load Regulation 0.7 % LOADREG V Input Voltage Range 2.5 5 V IN I Input Current V = 1.2V, SW = Open 1.5 2.5 mA S RUN Shutdown Current V = 0V, SW = Open 0.1 1 A RUN f Oscillator Frequency V 0.25V 1.2 1.5 1.8 MHz OSC REF V 0.1V 550 700 850 kHz REF V Bypass PFET Turn-Off Threshold V = 1.167 1.2 V REF REF Bypass PFET Turn-On Threshold V = 1.21 1.26 V REF R R of P-Channel FET I = 160mA, Wafer Level 0.3 0.4 PFET DS(ON) SW I = 160mA, DD Package 0.4 SW R R of N-Channel FET I = 160mA, Wafer Level 0.3 0.4 NFET DS(ON) SW I = 160mA, DD Package 0.4 SW R R of Bypass P-Channel FET I = 100mA, V = 3V, Wafer Level 0.05 0.08 BYPASS DS(ON) OUT IN I = 100mA, V = 3V, DD Package (Note 4) 0.08 OUT IN I SW Leakage V = 0V, V = 0V or 5V, V = 5V 0.01 1 A LSW RUN SW IN I Bypass PFET Leakage V = 0V, V = 5V, V = 0V 0.01 1 A LBYP OUT IN REF V RUN Threshold 0.3 1 1.5 V RUN I RUN Input Current V = 0V or 2.5V 0.01 1 A RUN RUN I REF Input Current 0.01 1 A REF Note 1: Absolute Maximum Ratings are those values beyond which the life temperature range are assured by design, characterization and correlation of a device may be impaired. with statistical process controls. Note 2: The LTC3408E is guaranteed to meet performance specifications Note 3: T is calculated from the ambient temperature T and power J A from 0C to 70C. Specifications over the 40C to 85C operating dissipation P according to the following formula: D LTC3408: T = T + (P )(43C/W) J A D 3408f 2 U WWW