LT1170/LT1171/LT1172
100kHz, 5A, 2.5A and 1.25A
High Efficiency Switching Regulators
FeaTures
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DescripTion
The
are monolithic high power-
switching 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, con-
trol 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.
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.
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 are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
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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.
Typical applicaTion
Boost Converter (5V to 12V)
5V
L1**
50µH
L2
10µH
C3
100µF
12V
1A
100
Maximum Output Power*
OUTPUT
FILTER
80
POWER (W)
**
BUCK-BOOST
V
O
= 30V
BOOST
FLYBACK
LT1170
*
ROUGH GUIDE ONLY. BUCK MODE
P
OUT
= (5A)(V
OUT
)
SPECIAL TOPOLOGIES DELIVER
MORE POWER.
** DIVIDE VERTICAL POWER SCALE
BY TWO FOR LT1171, BY FOUR
FOR LT1172.
LT1170/1/2 TA02
V
IN
V
SW
D1
MBR330
60
+
C3*
100µF
GND
LT1170
FB
V
C
R3
1k
C1
1µF
+
C2
1000µF
R1
10.7k
1%
40
20
R2
1.24k
1%
BUCK-BOOST
V
O
= 5V
0
10
30
20
INPUT VOLTAGE (V)
40
50
0
*REQUIRED IF INPUT LEADS
≥
2"
** COILTRONICS 50-2-52
PULSE ENGINEERING 92114
1170/1/2 TA01
117012fi
For more information
1
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