LT3570 Datasheet, PDF (1/20 Pages) Linear Technology – 1.5A Buck Converter, 1.5A Boost Converter and LDO Controller

FEATURES
n _{2.5V to 36V Input Voltage Range}
n _{Programmable Switching Frequency}
from 500kHz to 2MHz
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
APPLICATIONS
n _{Cable and Satellite Set-Top Boxes}
n _{Automotive Systems}
n _{Telecom Systems}
n _{“Dying Gasp” Systems}
n _{TFT LCD Displays}
LT3570
1.5A Buck Converter,
1.5A Boost Converter and
LDO Controller
DESCRIPTION
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.
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.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V_IN
5V
V_OUT1
12V
275mA
10μF
10μF
SHDN1
SHDN2
SHDN3
V_IN1 V_IN2 V_IN3 BIAS
SHDN1
SHDN2
SHDN3
BOOST
SW2
D1 ^6.8μH
143k
10.0k
10nF
22k
1nF
SW1
FB1
SS1
V_C1
FB2
SS2
V_C2
LT3570
NPN_DRV
FB3
R_T SYNC GND
15.8k
D3
100nF
3.3μH
D2
32.4k
22μF
22k
1nF
10nF 10.2k
V_OUT2
3.3V
1A
Q1
22.1k
10.2k
V_OUT3
2.5V
100mA
2.2μF
3570 TA01a
Efficiency
100
95
90
85
f_SW = 1.2MHz
80
VIN = 5V
V_OUT1 = 12V
V_OUT2 = 3.3V
75 ^VOUT3 ^{= 2.5V}
I_OUT1 = 275mA
I_OUT3 = 100mA
70
0
0.2 0.4 0.6
I_OUT2 (A)
0.8 1.0
3570 TA01b
3570fa
1