Datasheet LTC3854 (Analog Devices)

LTC3854 Small Footprint, Wide VIN Range Synchronous Step-Down DC/DC Controller
FEATURES DESCRIPTION
n
Wide Operating VIN Range: 4.5V to 38V
The LTC3854® is a high performance synchronous step- n
RSENSE or DCR Current Sensing
down switching DC/DC controller that drives an all N- 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 Output Current Foldback Limiting The RUN/SS pin provides both soft-start and enable (Disabled During Soft-Start) features. OPTI-LOOP compensation allows the transient n Output Overvoltage Protection response to be optimized over a wide range of output ca- n 5V LDO for External Gate Drive pacitance and ESR values. Current foldback limits MOSFET n OPTI-LOOP® Compensation Minimizes C dissipation during short circuit conditions. Current foldback OUT n Low Shutdown I functions are disabled during soft-start. Q: 15µA 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
APPLICATIONS
MOSFET drivers allow the use of high power external 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 n Telecom Systems of Linear Technology Corporation. All other trademarks are the property of their respective 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
VIN V 97 2.0 IN 6V TO 38V 47µF TG 50V EFFICIENCY 96 1.6 0.1µF LTC3854 0.1µF POWER LOSS (W) RUN/SS BOOST 4.7µH 95 1.2 ITH SW 2200pF AT 8.2mΩ DCR VOUT 100pF 5V 10k 7A 94 0.8 INTV 0.22µF + EFFICIENCY (%) CC 5.49k 150µF POWER LOSS 4.7µF 8.06k 93 0.4 FB BG 4.99k V 42.2k IN = 12V SENSE– 92 0 1 2 3 4 5 6 7 SENSE+ GND LOAD CURRENT (A) 3854 TA01b 3854 TA01 3854fb 1 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Revision History Related Parts