LT3581
3.3A Boost/Inverting DC/DC
Converter with Fault Protection
FeaTures
DescripTion
The LT®3581 is a PWM DC/DC converter with built-in fault
protection features to aid in protecting against output
shorts, input/output overvoltages, and overtemperature
conditions. The part consists of a 42V master switch, and
a 42V slave switch that can be tied together for a total
current limit of 3.3A.
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3.3A, 42V Combined Power Switch
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Master/Slave (1.9A/1.4A) Switch Design
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Output Short Circuit Protection
Wide Input Range: 2.5V to 22V Operating,
40V Maximum Transient
Switching Frequency Up to 2.5MHz
Easily Configurable as a Boost, SEPIC, Inverting or
Flyback Converter
User Configurable Undervoltage Lockout
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The LT3581 is ideal for many local power supply designs. It
canbeeasilyconfiguredinBoost,SEPIC,InvertingorFlyback
configurations, and is capable of generating 12V at 830mA,
or–12Vat625mAfroma5Vinput. Inaddition, theLT3581’s
slaveswitchallowstheparttobeconfiguredinhighvoltage,
high power charge pump topologies that are very efficient
and require fewer components than traditional circuits.
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Low V
Switch: 250mV at 2.75A (Typical)
CESAT
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Can be Synchronized to External Clock
Can Be Synchronized to other Switching Regulators
High Gain SHDN Pin Accepts Slowly Varying Input
Signals
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TheLT3581’sswitchingfrequencyrangecanbesetbetween
200kHz and 2.5MHz. The part may be clocked internally at
a frequency set by the resistor from the RT pin to ground,
or it may be synchronized to an external clock. A buffered
version of the clock signal is driven out of the CLKOUT
pin, and may be used to synchronize other compatible
switching regulator ICs to the LT3581.
14-Pin 4mm × 3mm DFN and 16-Lead MSE Packages
applicaTions
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Local Power Supply
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Vacuum Fluorescent Display (VFD) Bias Supplies
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TFT-LCD Bias Supplies
Automotive Engine Control Unit (ECU) Power
The LT3581 also features innovative SHDN pin circuitry
that allows for slowly varying input signals and an adjust-
able undervoltage lockout function. Additional features
such as frequency foldback and soft-start are integrated.
The LT3581 is available in 14-Pin 4mm × 3mm DFN and
16-Lead MSE packages.
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L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 7579816.
Efficiency and Power Loss vs
Load Current
Typical applicaTion
100
95
90
85
80
75
70
65
60
55
50
2000
1800
1600
1400
1200
1000
800
Output Short Protected, 5V to 12V Boost Converter Operating at 2MHz
1.5µH
V
OUT
V
IN
12V
5V
830mA
4.7µF
130k
6.04k
SW1 SW2
18.7k
V
FB
GATE
IN
100k
FAULT
V
IN
4.7µF
SHDN
CLKOUT
600
RT
V
C
LT3581
4.7µF
10k
400
56pF
SYNC
SS
10.5k
1nF
43.2k
200
GND
0.1µF
0
3581 TA01
0
200
600
LOAD CURRENT (mA)
800
1000
400
3581 TA01b
3581f
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