LINEAR LT3757 User Guide

LINEAR TECHNOLOGY JUNE 2009 VOLUME XIX NUMBER 2

IN THIS ISSUE… Two New Controllers for

COVER ARTICLE

Boost, Flyback, SEPIC

Two New Controllers for Boost, Flyback, SEPIC and Inverting DC/DC Converters Accept Inputs up to 100V

...........................................................1 and Inverting DC/DC

Wei Gu

Linear in the News… ...........................2 Converters Accept DESIGN FEATURES Charge Li-Ion Batteries Directly Inputs up to 100V by Wei Gu from High Voltage Automotive and Industrial Supplies Using Standalone Charger in a

Introduction

3mm × 3mm DFN .................................5 Jay Celani Two new versatile DC/DC controller rent of 1µA, making them an ideal fit

ICs, the LT®3757 and LT3758, are for battery-operated systems.

Power Management IC Combines

USB On-The-Go and USB Charging optimized for boost, flyback, SEPIC Both integrate a high voltage, low

in Compact Easy-to-Use Solution .........8 and inverting converter applications. dropout linear (LDO) regulator. Thanks George H. Barbehenn and Sauparna Das

The LT3757 operates over an input to a novel FBX pin architecture, the

Power Management IC with range of 2.9V to 40V, suitable for ap- LT3757 and LT3758 can be connected Pushbutton Control Generates

plications from single-cell lithium-ion directly to a divider from either the

Six Voltage Rails from USB or

2 AA Cells Via Low Loss battery portable electronics up to high positive output or the negative out-

Power Path™ Topology .......................12 voltage automotive and industrial put to ground. They also pack many John Canfield

power supplies. The LT3758 extends popular features such as soft-start,

Improve Hot Swap Performance and the input voltage to 100V, providing input undervoltage lockout, adjust- Save Design Time with Hot Swap™

flexible, high performance operation able frequency and synchronization

Controller that Integrates

2A MOSFET and Sense Resistor .........16 in high voltage, high power telecom- in a small 10-lead MSOP package or

David Soo munications equipment. Both ICs a 3mm × 3mm QFN package.

exhibit low shutdown quiescent cur- continued on page

Compact No RSENSE™ Controllers Feature Fast Transient Response

and Regulate to Low VOUT from

10V TO 30V

Wide Ranging VIN .........................................................18

4.7µF 200k VIN

Terry J. Groom 10µH IHLP-5050EZ-01

X5R SHDN/UVLO MBRM360

Space-Saving, Dual Output 48V

DC/DC Converter Yields LT3757

Plus/Minus Voltage Outputs SYNC GATE 590k

Si7850

with (Optional) I2C Programming .......22 1%

SENSE

Mathew Wich

RT SS FBX VC GND INTVCC

DESIGN IDEAS

(complete list on page 26) 50V

New Device Cameos ...........................37

Design Tools ......................................39

Sales Offices .....................................40 Figure 1. A 10V–30V input, 48V at 1A output boost converter

L, Linear Express, Linear Technology, LT, LTC, LTM, Bode CAD, Burst Mode, Filter CAD, LTspice, OPTI-LOOP, Over-The-Top, Poly Phase, Switcher CAD, µModule and the Linear logo are registered trademarks of Linear Technology Corporation. Adaptive Power, Bat-Track, C-Load, Direct Sense, Easy Drive, Filter View, Hot Swap, LTBi CMOS, LTCMOS, Linear View, Micropower Switcher CAD, Multimode Dimming, No Latency ∆Σ, No Latency Delta-Sigma, No RSENSE, Operational Filter, Panel Protect, Power Path, Power SOT, Safe Slot, Smart Start, SNEAK-A-BIT, Soft Span, Stage Shedding, Super Burst, Thin SOT, Timer Blox, Triple Mode, True Color PWM, Ultra Fast and VLDO are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.