LM3481MM electronics ic chips High Efficiency Low Side N Channel Controller

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 transient response in addition to cycle-by-cycle current limiting. Current limit can be programmed with a single external resistor.

The LM3481 has built in protection features such as thermal shutdown, short-circuit protection and over voltage protection. 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

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

V_IN pin Voltage -0.4V to 50V

FB Pin Voltage -0.4V to 6V

FA/SYNC/SD Pin Voltage -0.4V to 6V

COMP Pin Voltage -0.4V to 6V

UVLO Pin Voltage -0.4V to 6V

V_CC Pin Voltage -0.4V to 6V

DR Pin Voltage -0.4V to 6V

I_SEN Pin Voltage –0.4V to 600 mV

Peak Driver Output Current 1.0A

Power Dissipation Internally Limited

Storage Temperature Range −65°C to +150°C

Junction Temperature +150°C

ESD Susceptibilty

Human Body Model (Note 2) 2 kV

Lead Temperature

MM Package

Vapor Phase (60 sec.) 215°C

Infared (15 sec.) 220°C

Operating Ratings (Note 1)

Supply Voltage 2.97V to 48V

Junction Temperature Range −40°C to +125°C

Switching Frequency Range 100 kHz to 1 MHz

Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings indicates conditions for which the device is intended to be functional, but does not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions.

Note 2: The human body model is a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin

Typical Application Circuit

Connection Diagram

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