LT1170/LT1171/LT1172
100kHz, 5A, 2.5A and 1.25A
High Efficiency Switching Regulators
FeaTures
DescripTion
The LT®1170/LT1171/LT1172 are monolithic high power-
switching regulators. They can be operated in all standard
switching configurations including buck, boost, flyback,
forward,invertingand“Cuk.”Ahighcurrent,highefficiency
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Wide Input Voltage Range: 3V to 60V
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Low Quiescent Current: 6mA
Internal 5A Switch
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(2.5A for LT1171, 1.25A for LT1172)
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switch is included on the die along with all oscillator, con-
trol and protection circuitry. Integration of all functions
allowstheLT1170/LT1171/LT1172tobebuiltinastandard
5-pin TO-3 or TO-220 power package as well as the 8-pin
packages (LT1172). This makes them extremely easy to
use and provides “bust proof” operation similar to that
obtained with 3-pin linear regulators.
Shutdown Mode Draws Only 50µA Supply Current
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Very Few External Parts Required
Self-Protected Against Overloads
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Operates in Nearly All Switching Topologies
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Flyback-Regulated Mode Has Fully Floating Outputs
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Comes in Standard 5-Pin Packages
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LT1172 Available in 8-Pin MiniDIP and
Surface Mount Packages
The LT1170/LT1171/LT1172 operate with supply voltages
from 3V to 60V, and draw only 6mA quiescent current.
They can deliver load power up to 100W with no exter-
nal power devices. By utilizing current-mode switching
techniques, they provide excellent AC and DC load and
line regulation.
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Can Be Externally Synchronized
applicaTions
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Logic Supply 5V at 10A
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5V Logic to 15V Op Amp Supply
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Battery Upconverter
TheLT1170/LT1171/LT1172havemanyuniquefeaturesnot
found even on the vastly more difficult to use low power
controlchipspresentlyavailable.Theyuseadaptiveantisat
switch drive to allow very wide ranging load currents with
no loss in efficiency. An externally activated shutdown
mode reduces total supply current to 50µA typically for
standby operation.
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Power Inverter (+ to –) or (– to +)
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Fully Floating Multiple Outputs
USER NOTE:
This data sheet is only intended to provide specifications, graphs, and a general functional
description of the LT1170/LT1171/LT1172. Application circuits are included to show the capability
of the LT1170/LT1171/LT1172. A complete design manual (AN19) should be obtained to assist in
developing new designs. This manual contains a comprehensive discussion of both the LT1070
and the external components used with it, as well as complete formulas for calculating the values
of these components. The manual can also be used for the LT1170/LT1171/LT1172 by factoring in
the higher frequency. A CAD design program called SwitcherCAD is also available.
L, LT, LTC, LTM, Linear Technology, the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Typical applicaTion
Boost Converter (5V to 12V)
Maximum Output Power*
100
* ROUGH GUIDE ONLY. BUCK MODE
L1**
5V
L2
OUTPUT
FILTER
LT1170
P
= (5A)(V )
50µH
OUT
OUT
10µH
SPECIAL TOPOLOGIES DELIVER
MORE POWER.
80
60
40
20
0
C3
100µF
** DIVIDE VERTICAL POWER SCALE
BY TWO FOR LT1171, BY FOUR
FOR LT1172.
BUCK-BOOST
= 30V
D1
V
O
V
IN
MBR330
12V
1A
BOOST
V
SW
LT1170/1/2 TA02
FLYBACK
+
R1
C2
1000µF
10.7k
LT1170
+
1%
C3*
100µF
FB
V
C
GND
BUCK-BOOST
R2
1.24k
1%
V
= 5V
R3
1k
C1
1µF
O
0
10
20
30
40
50
INPUT VOLTAGE (V)
*REQUIRED IF INPUT LEADS ≥ 2"
** COILTRONICS 50-2-52
PULSE ENGINEERING 92114
1170/1/2 TA01
117012fi
1
For more information www.linear.com/LT1170