LT1371
500kHz High Efficiency
3A Switching Regulator
DESCRIPTION
FEATURES
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Faster Switching with Increased Efficiency The LT 1371 is a monolithic high frequency current mode
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Uses Small Inductors: 4.7H switching regulator. It can be operated in all standard
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All Surface Mount Components switching configurations including boost, buck, flyback,
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Low Minimum Supply Voltage: 2.7V forward, inverting and Cuk. A 3A high efficiency switch
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Quiescent Current: 4mA Typ is included on the die, along with all oscillator, control and
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Current Limited Power Switch: 3A protection circuitry.
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Regulates Positive or Negative Outputs
The LT1371 typically consumes only 4mA quiescent
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Shutdown Supply Current: 12A Typ
current and has higher efficiency than previous parts.
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Easy External Synchronization
High frequency switching allows for very small inductors
to be used.
U
APPLICATIONS
New design techniques increase flexibility and maintain
ease of use. Switching is easily synchronized to an exter-
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Boost Regulators
nal logic level source. A logic low on the Shutdown pin
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Laptop Computer Supplies
reduces supply current to 12A. Unique error amplifier
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Multiple Output Flyback Supplies
circuitry can regulate positive or negative output voltage
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Inverting Supplies
while maintaining simple frequency compensation tech-
niques. Nonlinear error amplifier transconductance re-
duces output overshoot on start-up or overload recovery.
Oscillator frequency shifting protects external compo-
nents during overload conditions.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
5V to 12V Boost Converter 12V Output Efficiency
D1
5V 100
L1*
V = 5V
MBRS330T3
IN
4.7H
V
OUT
12V
90
V
R1
IN
53.6k
ON
V
S/S SW
OFF
1%
80
LT1371
C4**
*
COILCRAFT DO3316P-472 (4.7H),
+ +
C1**
FB
22F
DO3316P-103 (10H) OR
22F
70
25V
GND V SUMIDA CD104-100MC (10
H)
25V C
2
**
R2
AVX TPSD226M025R0200
6.19k
60
MAX I
OUT
C2
1%
0.047F
L1
I
OUT
R3
C3
4.7H
0.7A
2k
0.0047F
50
10H 0.8A
0.01 0.1 1
LT1371 TA01
OUTPUT CURRENT (A)
LT1371 TA02
1
EFFICIENCY (%)
U
ULT1371
ABSOLUTEXAI U RATI GS
Supply Voltage ....................................................... 30V Operating Ambient Temperature Range ...... 0C to 70C
Switch Voltage Operating Junction Temperature Range
LT1371 ............................................................... 35V Commercial .......................................... 0C to 125C
LT1371HV .......................................................... 42V Industrial ......................................... 40C to 125C
S/S, SHDN, SYNC Pin Voltage ................................ 30V Short Circuit ......................................... 0C to 150C
Feedback Pin Voltage (Transient, 10ms) .............. 10V Storage Temperature Range ................ 65C to 150C
Feedback Pin Current........................................... 10mA Lead Temperature (Soldering, 10 sec)................. 300C
Negative Feedback Pin Voltage
(Transient, 10ms) ............................................. 10V
PACKAGE/ORDER I FOR ATIO
FRONT VIEW
ORDER PART ORDER PART
7
V
IN
NUMBER NUMBER
6
S/S
TAB
5
V
SW TOP VIEW
IS
4
GND
LT1371CSW
LT1371CR
GND 3
NFB
V
1
20
V
C SW
2
FB
LT1371HVCR LT1371HVCSW
FB
2
19
NC
1 V
C
LT1371ISW
LT1371IR
NFB
3
18
V
SW
R PACKAGE
LT1371HVIR LT1371HVISW
7-LEAD PLASTIC DD
GND
4
17
GND
T = 125C, = 30C/W
JMAX JA
GND
5
16
GND
2
WITH PACKAGE SOLDERED TO 0.5 INCH COPPER
GND
6
15
GND
AREA OVER BACKSIDE GROUND PLANE OR INTERNAL
POWER PLANE. CAN VARY FROM 20C/W TO
GND
7
14
GND
JA
>40C/W DEPENDING ON MOUNTING TECHNIQUE
SHDN
8
13
NC
SYNC
9
12
NC
ORDER PART
FRONT VIEW
V 10 11
GND
IN
NUMBER
7
V
IN
6
SW PACKAGE
S/S
TAB
5
20-LEAD PLASTIC SO WIDE
V
SW
LT1371CT7
IS
4
GND
T = 125C, = 50C/W
JMAX JA
GND 3
NFB
LT1371HVCT7
2
FB
WILL VARY FROM APPROXIMATELY 40C/W WITH
JA
1 LT1371IT7
V 2 2
C
0.75 INCH OF 1 OZ COPPER TO 50C/W WITH 0.33 INCH
OF 1 OZ COPPER ON A DOUBLE-SIDED BOARD
LT1371HVIT7
T7 PACKAGE
7-LEAD TO-220
T = 125C, = 50C/W, = 4C/W
JMAX JA JC
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
V = 5V, V = 0.6V, V = V , V , S/S, SHDN, SYNC and NFB pins open, unless otherwise noted.
IN C FB REF SW
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V Reference Voltage Measured at Feedback Pin 1.230 1.245 1.260 V
REF
V = 0.8V l 1.225 1.245 1.265 V
C
I Feedback Input Current V = V 250 550 nA
FB FB REF
l 900 nA
Reference Voltage Line Regulation 2.7V V 25V, V = 0.8V l 0.01 0.03 %/V
IN C
2
U WU
U W W W