LT3505
1.2A, Step-Down
Switching Regulator in
3mm
×
3mm DFN
FEATURES
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DESCRIPTION
The LT
®
3505 is a current mode PWM step-down DC/DC
converter with an internal 1.4A power switch. The wide
operating input range of 3.6V to 36V (40V maximum)
makes the LT3505 ideal for regulating power from a wide
variety of sources, including unregulated wall transform-
ers, 24V industrial supplies and automotive batteries. The
oscillator can be programmed for high frequency operation
allowing the use of tiny, low cost external components or
it can be programmed for lower frequency operation to
maximize efficiency.
Cycle-by-cycle current limit provides protection against
shorted outputs and soft-start eliminates input current
surge during start-up. The low current (<2µA) shutdown
mode provides output disconnect, enabling easy power
management in battery-powered systems.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
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Wide Input Range: 3.6V to 36V Operating,
40V Maximum
Up to 1.2A Output Current
Resistor-Programmable Fixed-Frequency Operation
from 200kHz to 3MHz
Output Adjustable Down to 780mV
Short-Circuit Robust
Uses Tiny Capacitors and Inductors
Soft-Start
Low Shutdown Current: <2µA
Low V
CESAT
Switch: 350mV at 1A
Thermally Enhanced, Low Profile 3mm x 3mm
DFN-8 and MSOP-8 Packages
APPLICATIONS
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Automotive Battery Regulation
Industrial Control Supplies
Wall Transformer Regulation
Distributed Supply Regulation
Battery-Powered Equipment
TYPICAL APPLICATION
750kHz, 3.3V Step-Down Converter
V
IN
4.2V TO 36V
ON OFF
V
IN
SHDN
LT3505
FB
R
T
75.0k
1µF
GND
V
C
69.8k
68pF
11.3k
10µF
BOOST
0.1µF 10µH
SW
36.5k
22pF
V
OUT
3.3V
1.1A, V
IN
> 5V
1.2A, V
IN
> 8V
EFFICIENCY (%)
90
85
80
75
70
65
60 V
IN
= 12V
V
OUT
= 3.3V
55 f
SW
= 750kHz
L = 10 H
50
0.8
0
0.2
0.4
0.6
LOAD CURRENT (A)
Efficiency
3505 TA01
1.0
1.2
3505fc
1
LINER [ LINEAR TECHNOLOGY ]
