LT3500
Monolithic 2A Step-Down
Regulator Plus Linear
Regulator/Controller
FEATURES
DESCRIPTION
The LT®3500 is a current mode PWM step-down DC/DC
converterwithaninternal2.3Aswitch.Thewideinputrange
of 3V to 40V makes the LT3500 suitable for regulating
power from a wide variety of sources, including automo-
tive batteries, 24V industrial supplies and unregulated
wall adapters.
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Wide Input Range: 3V to 36V Operating,
40V Maximum
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Short-Circuit Protected Over Full Input Range
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2A Output Current Capability
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Adjustable/Synchronizable Fixed Frequency
Operation from 250kHz to 2.2MHz
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Soft-Start/Tracking Capability
Resistor-programmable 250kHz to 2.2MHz frequency
range and synchronization capability enable optimization
between efficiency and external component size. Cycle-
by-cycle current limit, frequency foldback and thermal
shutdown provide protection against a shorted output.
The soft-start feature controls the ramp rate of the output
voltage, eliminating input current surge during start-up,
and also provides output tracking.
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Output Adjustable Down to 0.8V
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Adjustable Linear Regulator/Driver with 13mA
Output Capability
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Power Good Comparator with Complimentary
Outputs
Low Shutdown Current: 12μA
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Thermally Enhanced 3mm × 3mm DFN or 16-Pin
MSOP Package
The LT3500 contains an internal NPN transistor with feed-
back control which can be configured as a linear regulator
or as a linear regulator controller.
APPLICATIONS
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Automotive Battery Regulation
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Industrial Control
TheLT3500’slowcurrentshutdownmode(<12μA)enables
easy power management in battery-powered systems.
L, 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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Wall Transformer Regulation
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Distributed Power Regulation
TYPICAL APPLICATION
Dual Step-Down Converters
Switching Converter Efficiency
Output Voltage Ripple
90
85
80
75
70
65
60
55
50
V
IN
6V TO 36V
2.2μF
V
BST
SW
IN
0.47μF
6.8μH
LT3500
V
5V
1A
OUT1
V
= 5V AT 1A
AC COUPLED
2mV/DIV
OUT1
B240A
SHDN
SS
42.2k
22μF
0.47μF
FB
PG
PG
8.06k
V
= 3.3V AT 1A
AC COUPLED
2mV/DIV
OUT2
R
V
SYNC LDRV
T/
V
I
= 12V
= 0A
IN
OUT2
53.6k
330pF
C
1k
V
24.9k
8.06k
FREQUENCY = 800kHz
OUT2
3.3V
1A
LFB
3500 TA01c
500ns/DIV
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
40.2k
22μF
LOAD CURRENT (A)
3500 TA01b
3500 TA01a
3500fb
1