June 2, 2008

LM34919

Ultra Small 40V, 600 mA Constant On-Time Buck Switching

Regulator

General Description

The LM34919 Step Down Switching Regulator features all of

the functions needed to implement a low cost, efficient, buck

bias regulator capable of supplying 0.6A to the load. This buck

regulator contains an N-Channel Buck Switch, and is avail-

able in a micro SMD package. The constant on-time feedback

regulation scheme requires no loop compensation, results in

fast load transient response, and simplifies circuit implemen-

tation. The operating frequency remains constant with line

and load variations due to the inverse relationship between

the input voltage and the on-time. The valley current limit re-

sults in a smooth transition from constant voltage to constant

current mode when current limit is detected, reducing the fre-

quency and output voltage, without the use of foldback. Ad-

ditional features include: VCC under-voltage lockout, thermal

shutdown, gate drive under-voltage lockout, and maximum

duty cycle limiter.

Features

and input voltage

Typical Applications

Package

Basic Step Down Regulator

30004431

© 2008 National Semiconductor Corporation

300044

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