LM3481 Datasheet, PDF (1/22 Pages) National Semiconductor (TI) – High Efficiency Low-Side N-Channel Controller for Switching Regulators

November 16, 2007
LM3481
High Efficiency Low-Side N-Channel Controller for
Switching Regulators
General Description
The LM3481 is a versatile Low-Side N-FET high performance
controller for switching regulators. It is suitable for use in
topologies requiring a low-side FET, such as boost, flyback,
SEPIC, etc. The LM3481 can be operated at extremely high
switching frequencies in order to reduce the overall solution
size. The switching frequency of the LM3481 can be adjusted
to any value between 100 kHz and 1 MHz by using a single
external resistor or by synchronizing it to an external clock.
Current mode control provides superior bandwidth and tran-
sient response in addition to cycle-by-cycle current limiting.
Current limit can be programmed with a single external resis-
tor.
The LM3481 has built in protection features such as thermal
shutdown, short-circuit protection and over voltage protec-
tion. Power saving shutdown mode reduces the total supply
current to 5µA and allows power supply sequencing. Internal
soft-start limits the inrush current at start-up.
Key Specifications
■ ^{Wide supply voltage range of 2.97V to 48V}
■ ^{100 kHz to 1 MHz Adjustable and Synchronizable clock}
frequency
■ ^{±1.5% (over temperature) internal reference}
■ ^{10 µA shutdown current (over temperature)}
Features
■ ^{10-lead MSOP package}
■ ^{Internal push-pull driver with 1A peak current capability}
■ ^{Current limit and thermal shutdown}
■ ^{Frequency compensation optimized with a capacitor and}
a resistor
■ ^{Internal softstart}
■ ^{Current Mode Operation}
■ ^{Adjustable Undervoltage Lockout with Hysteresis}
■ ^{Pulse Skipping at Light Loads}
Applications
■ ^{Distributed Power Systems}
■ ^{Notebook, PDA, Digital Camera, and other Portable}
Applications
■ ^{Offline Power Supplies}
■ ^{Set-Top Boxes}
Typical Application Circuit
Typical SEPIC Converter
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