LT3740 Datasheet | Linear Technology

Features n n n n n n n n n n n n n LT3740 Wide Operating Range, Valley Mode, No RSENSE™ Synchronous Step-Down Controller DESCRIPTION The LT®3740 is a synchronous step-down switching regulator controller that drives N-channel power MOSFET stages. The controller uses valley current mode architecture to achieve very low duty cycles with excellent transient response without requiring a sense resistor. The LT3740 includes an internal step-up converter to provide a bias 7.8V higher than the input voltage for the drive. This enables the part to work from an input voltage as low as 2.2V. The XREF pin is an external reference input that allows the user to override the internal 0.8V feedback reference with any lower value, allowing full control of the output voltage during operation, output voltage tracking or soft-start. The LT3740 has three current limit levels that can be chosen by connecting the RANGE pin to ground, open, and input respectively. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Wide VIN Range: 2.2V to 22V Internal Boost Provides 6V Gate Drive For VIN Down to 2.2V No Sensing Resistor Required Dual N-Channel MOSFET Synchronous Drive Valley Current Mode Control Optimized for High Step-Down Ratio Power Good Output Voltage Monitor 0.8V Reference Three Pin-Selected Current Limit Levels Constant Switching Frequency: 300k Hz Programmable Soft-Start Output Voltage Tracking Available in 16-Pin 5mm × 3mm DFN APPLICATIONS n n n Notebook and Palmtop puters, PDA Portable Instruments Distributed Power Systems .. TYPICAL APPLICATION High Efficiency Step-Down Converter 22μH LT3740 SWB BGDP VIN SHDN 15k XREF 0.22μF 15k 20k 1n F BIAS TGATE 1Ω SW SN+ 1Ω BGATE - Efficiency vs Load Current VIN 3V to 12V 10μF 94 92 90 VIN = 3V VIN = 5V 1μF M1 HAT2168H EFFICIENCY (%) 1Ω 0.9μH VOUT 1.8V 10A 100μF...