LT1506 Datasheet, PDF (1/24 Pages) Linear Technology – 4.5A, 500kHz Step-Down Switching Regulator

LT1506
4.5A, 500kHz Step-Down
Switching Regulator
FEATURES
s _{Constant 500kHz Switching Frequency}
s _{Easily Synchronizable}
s _{Operates with Input as Low as 4V}
s _{Uses All Surface Mount Components}
s _{Inductor Size Reduced to 1.8µH}
s _{Saturating Switch Design: 0.07Ω}
s _{Shutdown Current: 20µA}
s _{Cycle-by-Cycle Current Limiting}
U
APPLICATIONS
s _{Portable Computers}
s _{Battery-Powered Systems}
s _{Battery Charger}
s _{Distributed Power}
DESCRIPTION
The LT^®1506 is a 500kHz monolithic buck mode switching
regulator functionally identical to the LT1374 but optimized
for lower input voltage applications. It will operate over a
4V to 15V input range compared with 5.5V to 25V for the
LT1374. 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 keeping quiescent supply current to 4mA and by utiliz-
ing a supply boost capacitor to saturate the power switch.
The LT1506 fits into standard 7-pin DD and fused lead
SO-8 packages. Full cycle-by-cycle short-circuit protection
and thermal shutdown are provided. Standard surface
mount external parts are used, including the inductor and
capacitors. There is the optional function of shutdown or
synchronization. A shutdown signal reduces supply current
to 20µA. Synchronization allows an external logic level sig-
nal to increase the internal oscillator from 580kHz to 1MHz.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
5V to 3.3V Down Converter
D2
1N914
INPUT
5V
10µF
C3
TO
+
50µF
CERAMIC
OPEN
OR
HIGH
= ON
C2
0.68µF
BOOST
V_IN
V_SW
LT1506-3.3
SHDN
SENSE
GND V_C
C_C
1.5nF
L1
5µH
OUTPUT
3.3V
4A
+
D1
MBRS330T3
C1
100µF, 10V
SOLID
TANTALUM
1506 TA01
Efficiency vs Load Current
90
V_OUT = 3.3V
V_IN = 5V
L = 10µH
85
80
75
70
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
LOAD CURRENT (A)
1506 TA02
1