LM3477

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SNVS141K – OCTOBER 2000 – REVISED MARCH 2013

LM3477 High Efficiency High-Side N-Channel Controller for Switching Regulator

Check for Samples: LM3477

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FEATURES

DESCRIPTION

The LM3477/A is a high-side N-channel MOSFET

2

•

500kHz Switching Frequency

switching regulator controller. It can be used in

•

Adjustable Current Limit

topologies requiring a high side MOSFET such as

•

1.5% Reference

buck, inverting (buck-boost) and zeta regulators. The

LM3477/A's

internal

push

pull

driver

allows

•

Thermal Shutdown

compatibility with a wide range of MOSFETs. This,

•

Frequency Compensation Optimized with a

the wide input voltage range, use of discrete power

Single Capacitor and Resistor

components and adjustable current limit allows the

•

Internal Softstart

LM3477/A to be optimized for a wide variety of

applications.

•

Current Mode Operation

•

Undervoltage Lockout with Hysteresis

The LM3477/A uses a high switching frequency of

500kHz to reduce the overall solution size. Current-

•

8-lead (VSSOP-8) Package

mode control requires only a single resistor and

capacitor for frequency compensation. The current

APPLICATIONS

mode architecture also yields superior line and load

•

Local Voltage Regulation

regulation and cycle-by-cycle current limiting. A 5µA

shutdown state can be used for power savings and

•

Distributed Power

for power supply sequencing. Other features include

•

Notebook and Palmtop Computers

internal soft-start and output over voltage protection.

•

Internet Appliances

The internal soft-start reduces inrush current. Over

voltage protection is a safety feature to ensure that

•

Printers and Office Automation

the output voltage stays within regulation.

•

Battery operated Devices

The LM3477A is similar to the LM3477. The primary

•

Cable Modems

difference between the two is the point at which the

•

Battery Chargers

device transitions into hysteretic mode. The hysteretic

threshold of the LM3477A is one-third of the LM3477.

Hysteretic Threshold(1)

LM3477

≊ 36% of programmed current limit

LM3477A

≊ 12% of programmed current limit

(1)

See Hysteretic Threshold and PROGRAMMING THE

CURRENT LIMIT/HYSTERETIC THRESHOLD for more

information.

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Products conform to specifications per the terms of the Texas

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necessarily include testing of all parameters.