8A and 10A High Efficiency
s Wide Input Voltage Range: 3.5V to 30V
s Low Quiescent Current: 7mA
s Internal 8A Switch (10A for LT1270A)
s Very Few External Parts Required
s Self-Protected Against Overloads
s Shutdown Mode Draws Only 100µA Supply Current
s Flyback-Regulated Mode Has Fully Floating Outputs
s Can be Externally Synchronized
(See LT1072 Data Sheet)
s Comes in Standard 5-Pin TO-220 Package
s High Efficiency Buck Converter
s PC Power Supply with Multiple Outputs
s Battery Upconverter
s Negative-to-Positive Converter
This data sheet is only intended to provide specifications, graphs and a general functional
description of the LT1270A/LT1270. Application circuits are included to show the capability of the
LT1270A/LT1270. A complete design manual (AN-19) should be obtained to assist in developing
new designs. AN-19 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. AN-19 can also be used for the LT1270A/LT1270 by factoring in the higher switch
current rating and higher operating frequency.
A comprehensive CAD program called SwitcherCad is also available. Contact the local sales office
in your area or the factory direct.
The LT1270A/LT1270 are monolithic high power switch-
ing regulators. Identical to the popular LT1070, except for
switching frequency (60kHz) and higher switch current,
they can be operated in all standard switching configura-
tions including buck, boost, flyback, and inverting. A high
current, high efficiency switch is included on the die along
with all oscillator, control, and protection circuitry. Inte-
gration of all functions allows the LT1270A/LT1270 to be
built in a standard TO-220 power package. This makes it
extremely easy to use and provides “bust proof” operation
similar to that obtained with 3-pin linear regulators.
The LT1270A/LT1270 operate with supply voltages from
3.5V to 30V, and draw only 7mA quiescent current. By
utilizing current-mode switching techniques, they provide
excellent AC and DC load and line regulation.
The LT1270A/LT1270 use adaptive anti-sat switch drive to
allow very wide ranging load currents with no loss in
efficiency. An externally activated shutdown mode re-
duces total supply current to 100µA typical for standby
High Efficiency† Buck Converter
(8V TO 25V)
†EFFICIENCY IS ≈ 88% @ 2A, 86% @ 5A.
FOR µPOWER SHUTDOWN OPTION, CONSULT FACTORY.
*THESE COMPONENTS RATED CONSERVATIVELY TO
IMPROVE EFFICIENCY. MAXIMUM OUTPUT CURRENT
CAN BE 7A. FOR HIGH EFFICIENCY, THE INDUCTOR SHOULD
BE MOLYPERMALLOY OR FERRITE.
LT1270 • TA01
Maximum Output Power*
VO = 12V
BUCK-BOOST, VO = 5V
0 5 10 15 20 25 30
INPUT VOLTAGE (V)
LT1270 • TA02
*MULTIPLY BY 1.2 FOR LT1270A.
BUCK MODE OUTPUT POWER ≈ (7.5A)(VOUT)
† TRANSFORMER TURNS RATIO MUST BE
OPTIMUM TO ACHIEVE FULL POWER