LT3570
1.5A Buck Converter,
1.5A Boost Converter and
LDO Controller
FEATURES
DESCRIPTION
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2.5V to 36V Input Voltage Range
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 2MHz
are programmed with an external timing resistor and the
oscillator can be synchronized to an external clock up to
2.75MHz.
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Programmable Switching Frequency
from 500kHz to 2MHz
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Synchronizable Up to 2.75MHz
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V
: 0.8V
OUT(MIN)
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Independent Soft-Start for Each Converter
Separate V Supplies for Each Converter
IN
Duty Cycle Range: 0% to 90% at 1MHz
Available in 24-Lead (4mm × 4mm) QFN and
20-Lead TSSOP Packages
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.
APPLICATIONS
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Cable and Satellite Set-Top Boxes
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
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Automotive Systems
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Telecom Systems
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“Dying Gasp” Systems
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TFT LCD Displays
TYPICAL APPLICATION
V
IN
5V
10μF
V
V
V
BIAS
IN1 IN2 IN3
D3
Efficiency
SHDN1
SHDN2
SHDN3
SHDN1
SHDN2
SHDN3
BOOST
100
100nF
V
3.3V
1A
OUT2
SW2
3.3μH
95
D2
32.4k
6.8μH
D1
V
OUT1
12V
275mA
90
85
SW1
FB2
SS2
22μF
143k
V
C2
LT3570
f
= 1.2MHz
= 5V
10μF
SW
IN
10.2k
FB1
SS1
22k
1nF
10nF
V
V
V
V
80
75
70
= 12V
10.0k
OUT1
OUT2
OUT3
OUT1
OUT3
V
C1
= 3.3V
= 2.5V
22k
1nF
I
I
= 275mA
= 100mA
NPN_DRV
Q1
V
OUT3
2.5V
0
0.2
0.4
I
OUT2
0.6
(A)
0.8
1.0
10nF
100mA
22.1k
3570 TA01b
FB3
2.2μF
R
T
SYNC
15.8k
GND
10.2k
3570 TA01a
3570fa
1