LT1072
1.25A High Efficiency
Switching Regulator
FEATURES
■ Available in MiniDiP, TO-220, and TO-3 Packages
■ Wide Input Voltage Range 3V to 60V
■ Low Quiescent Current—6mA
■ Internal 1.25A Switch
■ Very Few External Parts Required
■ Self-Protected Against Overloads
■ Operates in Nearly All Switching Topologies
■ Shutdown Mode Draws Only 50µA Supply Current
■ Flyback-Regulated Mode has Fully Floating Outputs
■ Can be Externally Synchronized
U
APPLICATIO S
■ Logic Supply 5V at 2.5A
■ 5V Logic to ±15V Op Amp Supply
■ Offline Converter up to 50W
■ Battery Upconverter
■ Power lnverter (+ to –) or (– to +)
■ Fully Floating Multiple Outputs
■ Driver for High Current Supplies
USER NOTE:
This data sheet is only intended to provide specifications, graphs, and a general functional
description of the LT1072. Application circuits are included to show the capability of the LT1072.
A complete design manual (AN-19) 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 LT1072 by factoring in the lower switch current rating.
, LTC and LT are registered trademarks of Linear Technology Corporation.
DESCRIPTIO
The LT®1072 is a monolithic high power switching
regulator. It 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, control, and
protection circuitry. Integration of all functions allows the
LT1072 to be built in a standard 5-pin TO-3 or TO-220
power package as well as the 8-pin miniDlP. This makes it
extremely easy to use and provides “bust proof” operation
similar to that obtained with 3-pin linear regulators.
The LT1072 operates with supply voltages from 3V to 60V,
and draws only 6mA quiescent current. It can deliver load
power up to 20 watts with no external power devices. By
utilizing current-mode switching techniques, it provides
excellent AC and DC load and line regulation.
The LT1072 has many unique features not found even on
the vastly more difficult to use low power control chips
presently available. It uses an adaptive anti-sat 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 typical for standby
operation. Totally isolated and regulated outputs can be
generated by using the optional “flyback regulation mode”
built into the LT1072, without the need for optocouplers or
extra transformer windings.
TYPICAL APPLICATIO
Boost Converter (5V to 12V)
5V 220µH**
VIN VSW
C3
25µF*
+
–
LT1072
GND VC FB
1k
+
1µF –
*REQUIRED IF INPUT LEADS ≥ 2”
**PULSE ENGINEERING 52626
10.7k
12V, 0.25A
1.24k
+
– 470µF
LT1072 • TA01
Maximum Output Power*
25
20
15
BOOST
10
BUCK-BOOST
VO = 30V
FLYBACK
ISOLATED
5
BUCK-BOOST
VO = 5V
0
0 10 20 30 40 50
INPUT VOLTAGE (V)
*ROUGH GUIDE ONLY. BUCK MODE POUT = 1A x VOUT.
MINIDIP OUTPUT POWER MAY BE LIMITED BY PACKAGE TEMPERATURE
RISE AT HIGH INPUT VOLTAGES OR HIGH DUTY CYCLES
LT1072 • TA02
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