LT1171_15 Datasheet, PDF (1/24 Pages) Linear Technology – 100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators

LT1170/LT1171/LT1172
100kHz, 5A, 2.5A and 1.25A
High Efficiency Switching Regulators
FEATURES
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}
APPLICATIONS
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.
DESCRIPTION
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.
TYPICAL APPLICATION
Boost Converter (5V to 12V)
5V
L1**
50μH
L2 _OUTPUT
10μH _FILTER
+ _C3*
100μF
V_IN
V_SW
LT1170
FB
GND
V_C
R3
1k
C1
1μF
D1
MBR330
C3
100μF
+
C2
1000μF
12V
R1 ^1A
10.7k
1%
R2
1.24k
1%
*REQUIRED IF INPUT LEADS r2"
** COILTRONICS 50-2-52
PULSE ENGINEERING 92114
1170/1/2 TA01
Maximum Output Power*
100
LT1170
80
60
BOOST
40
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
20
BUCK-BOOST
V_O = 5V
0
0
10
20
30
40
50
INPUT VOLTAGE (V)
117012fg
1