LT3581_15 Datasheet, PDF (1/36 Pages) Linear Technology – 3.3A Boost/Inverting DC/DC Converter with Fault Protection

LT3581
3.3A Boost/Inverting DC/DC
Converter with Fault Protection
FEATURES
n _{3.3A, 42V Combined Power Switch}
n _{Master/Slave (1.9A/1.4A) Switch Design}
n _{Output Short Circuit Protection}
n _{Wide Input Range: 2.5V to 22V Operating,}
40V Maximum Transient
n _{Switching Frequency Up to 2.5MHz}
n _{Easily Configurable as a Boost, SEPIC, Inverting or}
Flyback Converter
n _{User Configurable Undervoltage Lockout}
n _{Low VCESAT Switch: 250mV at 2.75A (Typical)}
n _{Can be Synchronized to External Clock}
n _{Can Be Synchronized to other Switching Regulators}
n _{High Gain SHDN Pin Accepts Slowly Varying Input}
Signals
n _{14-Pin 4mm × 3mm DFN and 16-Lead MSE Packages}
APPLICATIONS
n _{Local Power Supply}
n _{Vacuum Fluorescent Display (VFD) Bias Supplies}
n _{TFT-LCD Bias Supplies}
n _{Automotive Engine Control Unit (ECU) Power}
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.
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.
The LT3581 is ideal for many local power supply designs. It
can be easily configured in Boost, SEPIC, Inverting or Flyback
configurations, and is capable of generating 12V at 830mA,
or –12V at 625mA from a 5V input. In addition, the LT3581’s
slave switch allows the part to be configured in high voltage,
high power charge pump topologies that are very efficient
and require fewer components than traditional circuits.
The LT3581’s switching frequency range can be set bet­ween
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.
The LT3581 also features innovative SHDN pin circuitry that
allows for slowly varying input signals and an adjustable
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.
TYPICAL APPLICATION
Output Short Protected, 5V to 12V Boost Converter Operating at 2MHz
V_IN
5V
4.7µF
1.5µH
18.7k
10k
43.2k
100k
SW1 SW2
V_IN
FB
FAULT
GATE
SHDN
RT
SYNC
CLKOUT
LT3581 VC
SS
GND
4.7µF
130k
6.04k
V_OUT
12V
830mA
V_IN
56pF
0.1µF
10.5k
1nF
4.7µF
3581 TA01
For more information www.linear.com/LT3581
Efficiency and Power Loss vs
Load Current
100
2000
95
1800
90
1600
85
1400
80
1200
75
1000
70
800
65
600
60
400
55
200
50
0
0
200 400 600 800 1000
LOAD CURRENT (mA)
3581 TA01b
3581fb
1