LT1170/LT1171/LT1172
100kHz, 5A, 2.5A and 1.25A
High Efficiency Switching Regulators
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FEATURES
DESCRIPTIO
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Wide Input Voltage Range: 3V to 60V
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-
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Low Quiescent Current: 6mA
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Internal 5A Switch (2.5A for LT1171,
1.25A for LT1172)
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Shutdown Mode Draws Only 50µA Supply Current
Very Few External Parts Required
ciency switch is included on the die along with all oscilla-
tor, control and protection circuitry. Integration of all
functionsallowstheLT1170/LT1171/LT1172tobebuiltin
astandard5-pinTO-3orTO-220powerpackageaswellas
the 8-pin packages (LT1172). This makes them extremely
easy to use and provides “bust proof” operation similar to
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 that obtained with 3-pin linear regulators.
Packages
Can Be Externally Synchronized
The LT1170/LT1171/LT1172 operate with supply volt-
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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.
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APPLICATIO S
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Logic Supply 5V at 10A
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5V Logic to ±15V Op Amp Supply
The LT1170/LT1171/LT1172 have many unique features
not found even on the vastly more difficult to use low
powercontrolchipspresentlyavailable. Theyuseadaptive
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.
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Battery Upconverter
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Power Inverter (+ to –) or (– to +)
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Fully Floating Multiple Outputs
USER NOTE:
Thisdatasheetisonlyintendedtoprovidespecifications,graphs,andageneralfunctionaldescription
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. ThemanualcanalsobeusedfortheLT1170/LT1171/LT1172byfactoringinthehigher
frequency. A CAD design program called SwitcherCADTM is also available.
, LTC and LT are registered trademarks of Linear Technology Corporation.
SwitcherCAD is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATIO
Boost Converter (5V to 12V)
Maximum Output Power*
L1**
5V
L2
OUTPUT
FILTER
50µH
100
10µH
* ROUGH GUIDE ONLY. BUCK MODE
LT1170
P
= (5A)(V
)
OUT
OUT
C3
100µF
SPECIAL TOPOLOGIES DELIVER
MORE POWER.
80
60
40
20
0
D1
** DIVIDE VERTICAL POWER SCALE
BY TWO FOR LT1171, BY FOUR
FOR LT1172.
V
IN
MBR330
BUCK-BOOST
= 30V
12V
1A
V
SW
V
O
+
R1
BOOST
C2
1000µF
10.7k
LT1170/1/2 TA02
LT1170
FLYBACK
+
1%
C3*
100µF
FB
V
GND
C
R2
1.24k
1%
R3
1k
C1
1µF
BUCK-BOOST
V
O
= 5V
0
10
20
30
40
50
*REQUIRED IF INPUT LEADS ≥ 2"
** COILTRONICS 50-2-52
PULSE ENGINEERING 92114
INPUT VOLTAGE (V)
1170/1/2 TA01
117012ff
1