LT1374
4.5A, 500kHz Step-Down
Switching Regulator
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FEATURES
DESCRIPTIO
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Constant 500kHz Switching Frequency
TheLT®1374isa500kHzmonolithicbuckmodeswitching
regulator. A 4.5A switch is included on the die along with
allthenecessaryoscillator,controlandlogiccircuitry.High
switchingfrequencyallowsaconsiderablereductioninthe
sizeofexternalcomponents.Thetopologyiscurrentmode
for fast transient response and good loop stability. Both
fixed output voltage and adjustable parts are available.
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High Power 16-Pin TSSOP Package Available
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Uses All Surface Mount Components
Inductor Size Reduced to 1.8µH
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Saturating Switch Design: 0.07Ω
Effective Supply Current: 2.5mA
Shutdown Current: 20µA
Cycle-by-Cycle Current Limiting
Easily Synchronizable
Aspecialhighspeedbipolarprocessandnewdesigntech-
niquesachievehighefficiencyathighswitchingfrequency.
Efficiency is maintained over a wide output current range
by using the output to bias the circuitry and by utilizing a
supply boost capacitor to saturate the power switch.
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APPLICATIO S
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Portable Computers
TheLT1374isavailableinstandard7-pinDD,TO-220,fused
lead SO-8 and 16-pin exposed pad TSSOP packages. Full
cycle-by-cycle short-circuit protection and thermal shut-
downareprovided.Standardsurfacemountexternalparts
may be used, including the inductor and capacitors. There
is the optional function of shutdown or synchronization. A
shutdownsignalreducessupplycurrentto20µA.Synchro-
nizationallowsanexternallogiclevelsignaltoincreasethe
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Battery-Powered Systems
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Battery Chargers
Distributed Power
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internal oscillator from 580kHz to 1MHz.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
5V Buck Converter
Efficiency vs Load Current
D2
100
CMDSH3 OR FMMD914
V
V
= 5V
OUT
IN
= 10V
95
90
85
80
75
70
L = 10µH
C2
0.27µF
L1**
5µH
BOOST
OUTPUT**
5V, 4.25A
INPUT
V
V
IN
SW
6V TO 25V
+
C3*
LT1374-5 BIAS
10µF TO
50µF
DEFAULT
= ON
SHDN
SENSE
GND
V
C
C1
+
D1
100µF, 10V
SOLID
C
C
MBRS330T3
1.5nF
TANTALUM
* RIPPLE CURRENT RATING ≥ I /2
OUT
1374 TA01
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
LOAD CURRENT (A)
** INCREASE L1 TO 10µH FOR LOAD CURRENTS ABOVE 3.5A AND TO 20µH ABOVE 4A
SEE APPLICATIONS INFORMATION
1374 TA02
1374fb
1