LT1074/LT1076
Step-Down Switching
Regulator
ponents, are included on the chip. The topology is a classic
FEATURES
positive buck configuration but several design innova-
5A Onboard Switch (LT1074)
tions allow this device to be used as a positive-to-negative
Operates Up to 60V Input
converter, a negative boost converter, and as a flyback
100kHz Switching Frequency
converter. The switch output is specified to swing 40V
Greatly Improved Dynamic Behavior
below ground, allowing the LT1074 to drive a tapped-
Available in Low Cost 5 and 7-Lead Packages
inductor in the buck mode with output currents up to 10A.
Only 8.5mA Quiescent Current
The LT1074 uses a true analog multiplier in the feedback
Programmable Current Limit
loop. This makes the device respond nearly instanta-
Micropower Shutdown Mode
neously to input voltage fluctuations and makes loop gain
independent of input voltage. As a result, dynamic behav-
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APPLICATIO S ior of the regulator is significantly improved over previous
designs.
Buck Converter with Output Voltage Range of 2.5V
On-chip pulse by pulse current limiting makes the LT1074
to 50V
nearly bust-proof for output overloads or shorts. The input
Tapped-Inductor Buck Converter with 10A Output
voltage range as a buck converter is 8V to 60V, but a self-
at 5V
boot feature allows input voltages as low as 5V in the
Positive-to-Negative Converter
inverting and boost configurations.
Negative Boost Converter
Multiple Output Buck Converter
The LT1074 is available in low cost TO-220 or DD packages
with frequency pre-set at 100kHz and current limit at 6.5A
(LT1076 = 2.6A). A 7-pin TO-220 package is also available
DESCRIPTIO
which allows current limit to be adjusted down to zero. In
The LT 1074 is a 5A (LT1076 is rated at 2A) monolithic
addition, full micropower shutdown can be programmed.
bipolar switching regulator which requires only a few
See Application Note 44 for design details.
external parts for normal operation. The power switch, all
A fixed 5V output, 2A version is also available. See LT1076-5.
oscillator and control circuitry, and all current limit com-
, LTC and LT are registered trademarks of Linear Technology Corporation.
Buck Converter Efficiency
TYPICAL APPLICATIO
LT1074
Basic Positive Buck Converter
100
L1**
50H (LT1074)
V = 12V, V = 20V
OUT IN
100H (LT1076)
90
5V
V V
IN SW
5A * USE MBR340 FOR LT1076
10V TO 40V
** COILTRONICS #50-2-52 (LT1074) 80
LT1074 R1
MBR745*
#100-1-52 (LT1076)
V = 5V, V = 15V
2.8k OUT IN
PULSE ENGINEERING, INC.
1%
70
FB
#PE-92114 (LT1074)
GND V
C
#PE-92102 (LT1076)
R2
R3 L = 50H TYPE 52 CORE
60
HURRICANE #HL-AK147QQ (LT1074)
2.21k
2.7k DIODE = MBR735
#HL-AG210LL (LT1076)
1%
+ +
C3 C2 C1
RIPPLE CURRENT RATING I /2
OUT 50
200F 0.01F 500F
0 12 3 4 5 6
25V
OUTPUT LOAD CURRENT (A)
LT1074TA01 LT1074TPC27
sn1074 1074fds
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EFFICIENCY (%)
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ULT1074/LT1076
ABSOLUTE AXI U RATI GS
(Note 1)
Input Voltage I Pin Voltage (Forced) ............................................ 5.5V
LIM
LT1074/ LT1076 .................................................. 45V Maximum Operating Ambient Temperature Range
LT1074HV/LT1076HV ......................................... 64V Commercial .................................................0C to 70C
Switch Voltage with Respect to Input Voltage Industrial ................................................ 40C to 85C
LT1074/ LT1076 .................................................. 64V Military (OBSOLETE) .....................55C to 125C
LT1074HV/LT1076HV ......................................... 75V Maximum Operating Junction Temperature Range
Switch Voltage with Respect to Ground Pin (V Negative) Commercial ............................................... 0C to 125C
SW
LT1074/LT1076 (Note 7) ..................................... 35V Industrial .............................................. 40C to 125C
LT1074HV/LT1076HV (Note 7) ........................... 45V Military (OBSOLETE) .................... 55C to 150C
Feedback Pin Voltage..................................... 2V, +10V Maximum Storage Temperature ............... 65C to 150C
Shutdown Pin Voltage (Not to Exceed V ) .............. 40V Lead Temperature (Soldering, 10 sec)...................... 300C
IN
UUW
PACKAGE/ORDER I FOR ATIO
ORDER PART
FRONT VIEW ORDER PART
BOTTOM VIEW
V V
5 V NUMBER NUMBER
IN C IN
4 V
TAB IS SW
1
3 GND
GND LT1076CQ 2
LT1074CK
CASE
2 V
IS GND
C
LT1076IQ 3 LT1074HVCK
4
1 FB/SENSE
LT1074MK
Q PACKAGE
FB V
SW
LT1074HVMK
5-LEAD PLASTIC DD
K PACKAGE
LT1076CK
4-LEAD TO-3 METAL CAN
LT1076: = 4C, = 30C/W
JC JA
LT1076HVCK
LT1074: = 2.5C, = 35C/W
JC JA
LT1076: = 4C, = 35C/W
JC JA LT1076MK
LT1076CR
FRONT VIEW
LT1076HVMK
OBSOLETE PACKAGE
7 SHDN LT1076IR
Consider the T5 Package for Alternate Source
6 V
C
LT1076HVCR
TAB IS 5 FB/SENSE
4 GND
GND
LT1076HVIR
3 I
FRONT VIEW LT1074CT
LIM
2 V
SW
5 V LT1074HVCT
1 V IN
IN
4 V
SW
LT1074IT
R PACKAGE
TAB IS
7-LEAD PLASTIC DD 3 GND
LT1074HVIT
GND
2 V
C
LT1076: = 4C, = 30C/W
LT1076CT
JC JA
1
FB
LT1076HVCT
T PACKAGE
5-LEAD PLASTIC TO-220
LT1074CT7
LT1076IT
FRONT VIEW
LEADS ARE FORMED STANDARD FOR
LT1074HVCT7
LT1076HVIT
STRAIGHT LEADS, ORDER FLOW 06
SHDN
7
6 V
C
LT1074IT7
FB
5
TAB IS LT1074: = 2.5C, = 50C/W
JC JA
GND
4 LT1074HVIT7
LT1076: = 4C, = 50C/W
JC JA
GND I
3
LIM
V LT1076CT7
2
SW
1 V
IN
LT1076HVCT7
T7 PACKAGE
7-LEAD PLASTIC TO-220
LT1074: = 2.5C, = 50C/W
JC JA
LT1076: = 4C, = 50C/W
JC JA
2
*Assumes package is soldered to 0.5 IN of 1 oz. copper over internal ground plane or over back side plane.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
sn1074 1074fds
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