1FEATURES

2• 500kHz Switching Frequency

• Adjustable Current Limit

• 1.5% Reference

• Thermal Shutdown

• Frequency Compensation Optimized with a

Single Capacitor and Resistor

• Internal Softstart

• Current Mode Operation

• Undervoltage Lockout with Hysteresis

• 8-lead (VSSOP-8) Package

APPLICATIONS

• Local Voltage Regulation

• Distributed Power

• Notebook and Palmtop Computers

• Internet Appliances

• Printers and Office Automation

• Battery operated Devices

• Cable Modems

• Battery Chargers

DESCRIPTION

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

switching regulator controller. It can be used in

topologies requiring a high side MOSFET such as

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

LM3477/A's internal push pull driver allows

compatibility with a wide range of MOSFETs. This, the wide input voltage range, use of discrete power

components and adjustable current limit allows the

LM3477/A to be optimized for a wide variety of

applications.

The LM3477/A uses a high switching frequency of

500kHz to reduce the overall solution size. Currentmode

control requires only a single resistor and

capacitor for frequency compensation. The current mode architecture also yields superior line and load

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

shutdown state can be used for power savings and

for power supply sequencing. Other features include

internal soft-start and output over voltage protection.

The internal soft-start reduces inrush current. Over

voltage protection is a safety feature to ensure that

the output voltage stays within regulation.

The LM3477A is similar to the LM3477. The primary

difference between the two is the point at which the

device transitions into hysteretic mode. The hysteretic

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