
LT3570
1
3570fb
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
1.5A Buck Converter,
1.5A Boost Converter and
LDO Controller
The LT
3570 is a buck and boost converter with internal
power switches and LDO controller. Each converter is
designed with a 1.5A current limit and an input range from
2.5V to 36V, making the LT3570 ideal for a wide variety
of applications. Switching frequencies up to 2.1MHz are
programmed with an external timing resistor and the
oscillator can be synchronized to an external clock up to
2.75MHz.
The LT3570 features a programmable soft-start function
that limits the feedback voltage during start-up helping
prevent overshoot and limiting inrush current. The LDO
controller is capable of delivering up to 10mA of base
current to an external NPN transistor.
Efciency
n 2.5V to 36V Input Voltage Range
n Programmable Switching Frequency
from 500kHz to 2.1MHz
n Synchronizable Up to 2.75MHz
n VOUT(MIN): 0.8V
n Independent Soft-Start for Each Converter
n Separate VIN Supplies for Each Converter
n Duty Cycle Range: 0% to 90% at 1MHz
n Available in 24-Lead (4mm
× 4mm) QFN and
20-Lead TSSOP Packages
n Cable and Satellite Set-Top Boxes
n Automotive Systems
n Telecom Systems
n “Dying Gasp” Systems
n TFT LCD Displays
VIN1
SHDN1
SHDN2
SHDN3
SHDN1
SHDN2
SHDN3
SW1
FB1
100nF
1nF
10nF
22μF
2.2μF
VOUT3
2.5V
100mA
32.4k
VOUT2
3.3V
1A
22k
143k
VOUT1
12V
275mA
VIN
5V
22k
10.0k
10.2k
22.1k
10.2k
3570 TA01a
15.8k
10μF
1nF
10nF
3.3μH
6.8μH
D2
D3
D1
BOOST
SW2
FB2
SS2
NPN_DRV
FB3
VC2
SS1
VC1
VIN2 VIN3 BIAS
RT
SYNC
LT3570
GND
Q1
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
IOUT2 (A)
0
70
EFFICIENCY
(%)
75
80
85
90
95
100
0.2
0.4
0.6
0.8
3570 TA01b
1.0
fSW = 1.2MHz
VIN = 5V
VOUT1 = 12V
VOUT2 = 3.3V
VOUT3 = 2.5V
IOUT1 = 275mA
IOUT3 = 100mA