LT1
170/LT1
171/LT1172
100kHz, 5A, 2.5A and 1.25A
High Efficiency Switching Regulators
FEATURES
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DESCRIPTIO
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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
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, inverting and “Cuk.” A high current, high effi-
ciency switch is included on the die along with all oscilla-
tor, 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.
The LT1170/LT1171/LT1172 operate with supply volt-
ages 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 switch-
ing 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 cur-
rents with no loss in efficiency. An externally activated
shutdown mode reduces total supply current to 50µA
typically for standby operation.
, LTC and LT are registered trademarks of Linear Technology Corporation.
SwitcherCAD is a trademark of Linear Technology Corporation.
APPLICATIO S
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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
TM
is also available.
TYPICAL APPLICATIO
5V
L1**
50µH
Boost Converter (5V to 12V)
Maximum Output Power*
L2
10µH
C3
100µF
POWER (W)
**
OUTPUT
FILTER
100
LT1170
V
IN
V
SW
D1
MBR330
80
+
+
LT1170
C3*
100µF
GND
V
C
R3
1k
C1
1µF
*REQUIRED IF INPUT LEADS
≥
2"
FB
C2
1000µF
R1
10.7k
1%
12V
1A
60
BOOST
40
R2
1.24k
1%
20
BUCK-BOOST
V
O
= 5V
0
0
10
30
20
INPUT VOLTAGE (V)
40
50
** COILTRONICS 50-2-52
PULSE ENGINEERING 92114
1170/1/2 TA01
U
BUCK-BOOST
V
O
= 30V
FLYBACK
*
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
U
U
1
LINER [ LINEAR TECHNOLOGY ]
