LT1270

Manufacturer Part NumberLT1270
Description8A and 10A High Efficiency Switching Regulators
ManufacturerLinear Technology
LT1270 datasheet
 
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FEATURE
S
Wide Input Voltage Range: 3.5V to 30V
Low Quiescent Current: 7mA
Internal 8A Switch (10A for LT1270A)
Very Few External Parts Required
Self-Protected Against Overloads
Shutdown Mode Draws Only 100 A Supply Current
Flyback-Regulated Mode Has Fully Floating Outputs
Comes in Standard 5-Pin Package
Can be Externally Synchronized
(See LT1072 Data Sheet)
O
U
PPLICATI
S
A
High Efficiency Buck Converter
PC Power Supply with Multiple Outputs
Battery Upconverter
Negative-to-Positive Converter
USER NOTE:
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.
U
O
TYPICAL
A
PPLICATI
High Efficiency
V
IN
V
SW
(8V TO 25V)
1N5819
LT1270*
V
FB
IN
GND
V
C
+
1 F
0.047 F
1k
+
470 F
MBR1035*
35V
2N3904
8A and 10A High Efficiency
D
ESCRIPTIO
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 100 A typical for standby
operation.
Buck Converter
EFFICIENCY IS 88% @ 2A, 86% @ 5A.
FOR
POWER 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.
0.047 F
35 H, 8A*
5V*
5A
9.1k
ANODE
LT1431CZ
REF
CATHODE
10k
1N4158
1000 F
360
560
25V
LT1270 • TA01
LT1270A/LT1270
Switching Regulators
U
Maximum Output Power*
100
BOOST
80
BUCK-BOOST,
V
= 12V
O
(INVERTING)
60
FLYBACK
40
BUCK-BOOST, V
= 5V
20
O
(INVERTING)
0
0
5
15
20
25
30
10
INPUT VOLTAGE (V)
LT1270 • TA02
*MULTIPLY BY 1.2 FOR LT1270A.
BUCK MODE OUTPUT POWER (7.5A)(V
)
OUT
TRANSFORMER TURNS RATIO MUST BE
OPTIMUM TO ACHIEVE FULL POWER
1

LT1270 Summary of contents

  • Page 1

    ... 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 ...

  • Page 2

    ... XI U Supply Voltage ....................................................... 30V Switch Output Voltage ............................................ 60V Feedback Pin Voltage (Transient, 1ms) ................ 15V Operating Junction Temperature Range LT1270AC/LT1270C (Oper.)................ 125 C LT1270AC/LT1270C (Short-Ckt) ......... 140 C Storage Temperature Range ................ – 150 C Lead Temperature (Soldering, 10 sec)................ 300 C ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER V ...

  • Page 3

    ... MIN TYP MAX 10.0 16.0 7.5 14 1.5 100 400 100 150 250 50 300 = 6.67 (1.7 – DC) for the LT1270 and I LIM Switch Saturation Voltage 1 25°C J 1.2 0.8 0 SWITCH CURRENT (A) LT1270 • TA04 UNITS mA/A kHz kHz % s ...

  • Page 4

    ... V SW MBR1020 12V, 2A LT1270 10. GND V C 1000 F 25V 1k 1.24k + 1 F PULSE ENGINEERING #PE-92116 LT1270 • TA05 + C3 100 F* OPTIONAL INPUT FILTER –20V PACKAGE DESCRIPTIO 0.380 – 0.420 (9.652 – 10.668) 0.139 – 0.153 (3.531 – 3.886) DIA 0.560 – 0.650 (14.224 – ...