LT3500
1
3500fc
FEATURES
APPLICATIONS
DESCRIPTION
Monolithic 2A Step-Down
Regulator Plus Linear
Regulator/Controller
The LT3500 is a current mode PWM step-down DC/DC
converter with an internal 2.3A switch. The wide input range
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.
Resistor-programmable 250kHz to 2.2MHz frequency
range and synchronization capability enable optimization
between efciency 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.
The LT3500 contains an internal NPN transistor with feed-
back control which can be congured as a linear regulator
or as a linear regulator controller.
The LT3500’s low current shutdown mode (<12μA) enables
easy power management in battery-powered systems.
n Wide Input Range: 3V to 36V Operating,
40V Maximum
n Short-Circuit Protected Over Full Input Range
n 2A Output Current Capability
n Adjustable/Synchronizable Fixed Frequency
Operation from 250kHz to 2.2MHz
n Soft-Start/Tracking Capability
n Output Adjustable Down to 0.8V
n Adjustable Linear Regulator/Driver with 13mA
Output Capability
n Power Good Comparator with Complimentary
Outputs
n Low Shutdown Current: 12μA
n Thermally Enhanced 3mm
× 3mm DFN or 16-Pin
MSOP Package
n Automotive Battery Regulation
n Industrial Control
n Wall Transformer Regulation
n Distributed Power Regulation
Dual Step-Down Converters
Output Voltage Ripple
Switching Converter Efciency
6.8μH
0.47μF
22μF
42.2k
8.06k
2.2μF
0.47μF
VIN
6V TO 36V
40.2k
53.6k
330pF
3500 TA01a
VOUT1
5V
1A
VOUT2
3.3V
1A
B240A
BST
VIN
SW
FB
SHDN
SS
LT3500
RT/SYNC
VC
LDRV
LFB
PG
8.06k
24.9k
1k
LOAD CURRENT (A)
0
EFFICIENCY
(%)
90
85
80
75
70
65
60
55
50
1.6
3500 TA01b
0.4
0.8
1.2
2.0
1.4
0.2
0.6
1.0
1.8
VIN = 12V
IOUT2 = 0A
FREQUENCY = 800kHz
500ns/DIV
3500 TA01c
VOUT1 = 5V AT 1A
AC COUPLED
2mV/DIV
VOUT2 = 3.3V AT 1A
AC COUPLED
2mV/DIV
TYPICAL APPLICATION
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Technology Corporation. All other trademarks are the property of their respective owners.