LT1170/LT1171/LT1172
100kHz, 5A, 2.5A and 1.25A
High Efficiency Switching Regulators
FEATURES
DESCRIPTION
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The LT®1170/LT1171/LT1172 are monolithic high powerswitching regulators. They can be operated in all standard
switching configurations including buck, boost, flyback,
forward, inverting and “Cuk.” A high current, high efficiency
switch is included on the die along with all oscillator, control and protection circuitry. Integration of all functions
allows the LT1170/LT1171/LT1172 to be built in a standard
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.
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Wide Input Voltage Range: 3V to 60V
Low Quiescent Current: 6mA
Internal 5A Switch
(2.5A for LT1171, 1.25A for LT1172)
Shutdown Mode Draws Only 50μA Supply Current
Very Few External Parts Required
Self-Protected Against Overloads
Operates in Nearly All Switching Topologies
Flyback-Regulated Mode Has Fully Floating Outputs
Comes in Standard 5-Pin Packages
LT1172 Available in 8-Pin MiniDIP and
Surface Mount Packages
Can Be Externally Synchronized
APPLICATIONS
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Logic Supply 5V at 10A
5V Logic to ±15V Op Amp Supply
Battery Upconverter
Power Inverter (+ to –) or (– to +)
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.
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 external power devices. By utilizing current-mode switching
techniques, they provide excellent AC and DC load and
line regulation.
The LT1170/LT1171/LT1172 have many unique features not
found even on the vastly more difficult to use low power
control chips presently available. They use adaptive antisat
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.
L, LT, LTC, LTM, Linear Technology, the Linear logo and SwitcherCAD are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
TYPICAL APPLICATION
Boost Converter (5V to 12V)
L1**
50μH
D1
MBR330
VIN
VSW
+
L2
10μH
LT1170
C3*
100μF
+
OUTPUT
FILTER
80
C3
100μF
C2
1000μF
* ROUGH GUIDE ONLY. BUCK MODE
POUT = (5A)(VOUT)
SPECIAL TOPOLOGIES DELIVER
MORE POWER.
** DIVIDE VERTICAL POWER SCALE
BY TWO FOR LT1171, BY FOUR
FOR LT1172.
LT1170
R1
10.7k
1%
12V
1A
POWER (W) **
5V
Maximum Output Power*
100
BUCK-BOOST
VO = 30V
60
BOOST
LT1170/1/2 TA02
FLYBACK
40
FB
GND
20
VC
R3
1k
C1
1μF
*REQUIRED IF INPUT LEADS
2"
** COILTRONICS 50-2-52
PULSE ENGINEERING 92114
R2
1.24k
1%
BUCK-BOOST
VO = 5V
0
0
10
30
20
INPUT VOLTAGE (V)
40
50
1170/1/2 TA01
117012fg
1
