Datasheet LT3570 (Analog Devices)

LT3570 1.5A Buck Converter, 1.5A Boost Converter and LDO Controller
FEATURES DESCRIPTION
n
2.5V to 36V Input Voltage Range
The LT®3570 is a buck and boost converter with internal n
Programmable Switching Frequency
power switches and LDO controller. Each converter is
from 500kHz to 2.1MHz
designed with a 1.5A current limit and an input range from n
Synchronizable Up to 2.75MHz
2.5V to 36V, making the LT3570 ideal for a wide variety n VOUT(MIN): 0.8V of applications. Switching frequencies up to 2.1MHz are n Independent Soft-Start for Each Converter programmed with an external timing resistor and the n Separate VIN Supplies for Each Converter oscillator can be synchronized to an external clock up to n Duty Cycle Range: 0% to 90% at 1MHz 2.75MHz. n Available in 24-Lead (4mm × 4mm) QFN and The LT3570 features a programmable soft-start function 20-Lead TSSOP Packages that limits the feedback voltage during start-up helping prevent overshoot and limiting inrush current. The LDO
APPLICATIONS
controller is capable of delivering up to 10mA of base current to an external NPN transistor. n Cable and Satellite Set-Top Boxes n Automotive Systems L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. n Telecom Systems n “Dying Gasp” Systems n TFT LCD Displays
TYPICAL APPLICATION
VIN 5V 10μF VIN1 VIN2 VIN3 BIAS D3
Effi ciency
SHDN1 SHDN1 BOOST SHDN2 SHDN2 100nF 100 VOUT2 SHDN3 SHDN3 SW2 3.3V 3.3μH 1A D2 95 32.4k 6.8μH D1 VOUT1 12V SW1 FB2 90 275mA SS2 22μF 143k VC2 85 LT3570 10μF FB1 22k 10nF 10.2k fSW = 1.2MHz V SS1 EFFICIENCY (%) 80 IN = 5V 10.0k VOUT1 = 12V V 1nF C1 VOUT2 = 3.3V 22k 75 VOUT3 = 2.5V IOUT1 = 275mA NPN_DRV Q1 I V OUT3 = 100mA 1nF OUT3 70 2.5V 0 0.2 0.4 0.6 0.8 1.0 10nF 100mA 22.1k IOUT2 (A) FB3 2.2μF 3570 TA01b RT SYNC GND 10.2k 15.8k 3570 TA01a 3570fb 1