LT3740 Wide Operating Range, Valley Mode, No R SENSE Synchronous Step-Down Controller FEATURES DESCRIPTION n Wide V Range: 2.2V to 22V The LT 3740 is a synchronous step-down switching IN n Internal Boost Provides 6V Gate Drive regulator controller that drives N-channel power MOSFET For V Down to 2.2V stages. The controller uses valley current mode architecture IN n No Sensing Resistor Required to achieve very low duty cycles with excellent transient n Dual N-Channel MOSFET Synchronous Drive response without requiring a sense resistor. n Valley Current Mode Control The LT3740 includes an internal step-up converter to n Optimized for High Step-Down Ratio provide a bias 7.8V higher than the input voltage for the n Power Good Output Voltage Monitor drive. This enables the part to work from an input voltage n 0.8V Reference as low as 2.2V. n Three Pin-Selected Current Limit Levels n The XREF pin is an external reference input that allows the Constant Switching Frequency: 300kHz n user to override the internal 0.8V feedback reference with Programmable Soft-Start n any lower value, allowing full control of the output voltage Output Voltage Tracking n during operation, output voltage tracking or soft-start. Available in 16-Pin 5mm 3mm DFN The LT3740 has three current limit levels that can be chosen by connecting the RANGE pin to ground, open, APPLICATIONS and input respectively. n Notebook and Palmtop Computers, PDA L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. n No R is a trademark of Linear Technology Corporation. All other trademarks are the Portable Instruments SENSE property of their respective owners. n Distributed Power Systems TYPICAL APPLICATION High Ef ciency Step-Down Converter Ef ciency vs Load Current V IN 94 3V to 12V 1F 22H LT3740 92 10F SWB BGDP V = 5V IN V = 3V IN BIAS V 90 IN 1 M1 TGATE HAT2168H SHDN 88 0.9H V 1 OUT SW 1.8V 15k 86 V = 12V 10A IN + XREF SN D1 100F 84 1 B320A M2 s 3 BGATE HAT2165H 0.22F 82 39pF V = 1.8V OUT 15k SN 80 105k V C 0 2 46 8 10 PGND 20k LOAD CURRENT (A) RANGE GND FB 3740 TA01b 1nF 80.6k 22pF 3740 TA01a 3740fc 1 EFFICIENCY (%)LT3740 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW SN , BGATE, V , FB, XREF, PGOOD Voltages .............10V C SN 1 16 V C V ,SHDN, SW, Range Voltages ...............................22V IN + PGND 2 15 FB BIAS, TGATE, BGDP, SN Voltages ............................32V BGATE 3 14 XREF SWB Voltage ............................................................36V BGDP 4 13 SHDN Maximum Junction Temperature........................... 125C 17 + SN 5 12 PGOOD Operating Temperature Range (Note 2)....40C to 85C SW 6 11 RANGE Storage Temperature Range ...................65C to 125C TGATE 7 10 V IN BIAS 8 9 SWB DHC PACKAGE 16-LEAD (5mm 3mm) PLASTIC DFN T = 125C, = 43C/W JMAX JA EXPOSED PAD IS GND (PIN 17), MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3740EDHC PBF LT3740EDHC TRPBF 3740 40C to 85C 16-Lead (5mm 3mm) Plastic DFN LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3740EDHC LT3740EDHC TR 3740 16-Lead (5mm 3mm) Plastic DFN 40C to 85C Consult LTC Marketing for parts speci ed with wider operating temperature ranges. For more information on lead free part marking, go to: