Datasheet
LT1170/LT1171/LT1172
1
117012fg
TYPICAL APPLICATION
FEATURES DESCRIPTION
100kHz, 5A, 2.5A and 1.25A
High Efficiency Switching Regulators
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 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 and SwitcherCAD are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
Boost Converter (5V to 12V)
APPLICATIONS
n
Wide Input Voltage Range: 3V to 60V
n
Low Quiescent Current: 6mA
n
Internal 5A Switch
(2.5A for LT1171, 1.25A for LT1172)
n
Shutdown Mode Draws Only 50μA Supply Current
n
Very Few External Parts Required
n
Self-Protected Against Overloads
n
Operates in Nearly All Switching Topologies
n
Flyback-Regulated Mode Has Fully Floating Outputs
n
Comes in Standard 5-Pin Packages
n
LT1172 Available in 8-Pin MiniDIP and
Surface Mount Packages
n
Can Be Externally Synchronized
n
Logic Supply 5V at 10A
n
5V Logic to ±15V Op Amp Supply
n
Battery Upconverter
n
Power Inverter (+ to –) or (– to +)
n
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.
Maximum Output Power*
1170/1/2 TA01
D1
MBR330
C2
1000µF
C1
1µF
R1
10.7k
1%
R2
1.24k
1%
LT1170
GND
V
IN
5V
R3
1k
*REQUIRED IF INPUT LEADS r2"
** COILTRONICS 50-2-52
PULSE ENGINEERING 92114
V
SW
FB
V
C
OUTPUT
FILTER
L2
10µH
L1**
50
µH
C3
100µF
12V
1A
C3*
100µF
+
+
INPUT VOLTAGE (V)
0
POWER (W) **
100
80
60
40
20
0
40
LT1170/1/2 TA02
10
20
30
50
* 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.
BOOST
BUCK-BOOST
V
O
= 30V
FLYBACK
BUCK-BOOST
V
O
= 5V
LT1170