LT1374
4.5A, 500kHz Step-Down
Switching Regulator
FEATURES
s
s
s
s
s
s
s
s
s
DESCRIPTIO
Constant 500kHz Switching Frequency
High Power 16-Pin TSSOP Package Available
Uses All Surface Mount Components
Inductor Size Reduced to 1.8
µ
H
Saturating Switch Design: 0.07Ω
Effective Supply Current: 2.5mA
Shutdown Current: 20µA
Cycle-by-Cycle Current Limiting
Easily Synchronizable
The LT
®
1374 is a 500kHz monolithic buck mode switching
regulator. A 4.5A switch is included on the die along with
all the necessary oscillator, control and logic circuitry. High
switching frequency allows a considerable reduction in the
size of external components. The topology is current mode
for fast transient response and good loop stability. Both
fixed output voltage and adjustable parts are available.
A special high speed bipolar process and new design tech-
niques achieve high efficiency at high switching frequency.
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.
The LT1374 is available in standard 7-pin DD, TO-220, fused
lead SO-8 and 16-pin exposed pad TSSOP packages. Full
cycle-by-cycle short-circuit protection and thermal shut-
down are provided. Standard surface mount external parts
may be used, including the inductor and capacitors. There
is the optional function of shutdown or synchronization. A
shutdown signal reduces supply current to 20µA. Synchro-
nization allows an external logic level signal to increase the
internal oscillator from 580kHz to 1MHz.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
Portable Computers
Battery-Powered Systems
Battery Chargers
Distributed Power
TYPICAL APPLICATIO
5V Buck Converter
D2
CMDSH3 OR FMMD914
C2
0.27µF
INPUT
6V TO 25V
V
IN
BOOST
V
SW
100
95
C3*
10µF TO
50µF
+
DEFAULT
= ON
OUTPUT**
5V, 4.25A
EFFICIENCY (%)
L1**
5µH
90
85
80
75
70
0
0.5
1.0
1.5 2.0 2.5 3.0
LOAD CURRENT (A)
3.5
4.0
LT1374-5 BIAS
SHDN
GND
SENSE
V
C
C
C
1.5nF
D1
MBRS330T3
+
C1
100µF, 10V
SOLID
TANTALUM
1374 TA01
* RIPPLE CURRENT RATING
≥
I
OUT
/2
** INCREASE L1 TO 10µH FOR LOAD CURRENTS ABOVE 3.5A AND TO 20µH ABOVE 4A
SEE APPLICATIONS INFORMATION
U
Efficiency vs Load Current
V
OUT
= 5V
V
IN
= 10V
L = 10µH
1374 TA02
U
U
1374fb
1
LINER [ LINEAR TECHNOLOGY ]
