POWER LOSS (W) LTC3854 Small Footprint, Wide V Range Synchronous IN Step-Down DC/DC Controller FEATURES DESCRIPTION n Wide Operating V Range: 4.5V to 38V The LTC3854 is a high performance synchronous step- IN n R or DCR Current Sensing down switching DC/DC controller that drives an all N- SENSE n 1% 0.8V Reference Accuracy Over Temperature channel synchronous power MOSFET stage. n 400kHz Switching Frequency The LTC3854 features a 400kHz constant frequency current n Dual N-channel MOSFET Synchronous Drive mode architecture. The LTC3854 operates from a 4.5V to n Very Low Dropout Operation: 97% Duty Cycle 38V (40V absolute maximum) input voltage range and n Starts Up Into Pre-Biased Output regulates the output voltage from 0.8V to 5.5V. n Adjustable Output Voltage Soft-Start n The RUN/SS pin provides both soft-start and enable Output Current Foldback Limiting features. OPTI-LOOP compensation allows the transient (Disabled During Soft-Start) n response to be optimized over a wide range of output ca- Output Overvoltage Protection n pacitance and ESR values. Current foldback limits MOSFET 5V LDO for External Gate Drive n dissipation during short circuit conditions. Current foldback OPTI-LOOP Compensation Minimizes C OUT n functions are disabled during soft-start. Low Shutdown I : 15A Q n Tiny Thermally Enhanced 12-Pin 2mm 3mm DFN The LTC3854 has a minimum on-time at 75ns, making it and MSOP Packages well suited for high step-down ratios. The strong onboard MOSFET drivers allow the use of high power external APPLICATIONS MOSFETs to produce output currents up to 20A. n Automotive Systems L, LT, LTC, LTM, Linear Technology, the Linear logo and OPTI-LOOP are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective n Telecom Systems owners. Protected by U.S. Patents, including 5705919, 6498466, 5408150, 6222231. n Industrial Equipment n Distributed DC Power Systems TYPICAL APPLICATION High Efficiency Synchronous Step-Down Converter Efficiency and Power Loss vs Load Current V 97 2.0 IN V IN 6V TO 38V 47F TG EFFICIENCY 50V 96 1.6 LTC3854 0.1F 0.1F RUN/SS BOOST 95 1.2 4.7H ITH SW AT 8.2m DCR V OUT 2200pF 5V 100pF 94 0.8 10k 7A 0.22F + INTV CC POWER LOSS 5.49k 150F 4.7F 8.06k 93 0.4 FB BG 4.99k V = 12V IN 42.2k SENSE 92 0 1 2 3 4 5 6 7 + SENSE GND LOAD CURRENT (A) 3854 TA01b 3854 TA01 3854fb 1 EFFICIENCY (%)LTC3854 (Note 1) ABSOLUTE MAXIMUM RATINGS Input Supply Voltage (V ) ........................ 40V to 0.3V ITH, FB Voltages ....................................... 2.7V to 0.3V IN Top Side Driver Voltage (BOOST) ............... 46V to 0.3V INTV Peak Output Current (Note 8) ....................40mA CC Switch Voltage (SW) .................................. 40V to 5.0V Operating Temperature Range INTV , BOOST-SW .................................... 6V to 0.3V (Notes 2, 3) ..........................................40C to 85C CC + SENSE , SENSE ......................................... 6V to 0.3V Maximum Junction Temperature ...................... 125C RUN/SS ........................................................ 6V to 0.3V Storage Temperature Range .................. 65C to 125C PIN CONFIGURATION TOP VIEW TOP VIEW + 1 FB 12 SENSE + FB 1 12 SENSE ITH 2 SENSE 11 ITH 2 11 SENSE RUN/SS 3 10 V RUN/SS 3 10 V IN IN 13 13 BOOST 4 9 INTV BOOST 4 9 INTV CC CC TG 5 8 BG TG 8 BG 5 SW 6 7 GND SW 6 7 GND MSE PACKAGE DDB PACKAGE 12-LEAD PLASTIC MSOP 12-LEAD (3mm 2mm) PLASTIC DFN T = 125C, = 40C/W, = 16C/W JMAX JA JC T = 125C, = 76C/W, = 10C/W EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB JMAX JA JC EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3854EDDB PBF LTC3854EDDB TRPBF LDPC 40C to 85C 12-Lead (3mm 2mm) Plastic DFN LTC3854IDDB PBF LTC3854IDDB TRPBF LDPC 12-Lead (3mm 2mm) Plastic DFN 40C to 85C LTC3854EMSE PBF LTC3854EMSE TRPBF 3854 12-Lead Plastic MSOP 40C to 85C LTC3854IMSE PBF LTC3854IMSE TRPBF 3854 12-Lead Plastic MSOP 40C to 85C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: