LM34919 Datasheet, PDF (1/18 Pages) National Semiconductor (TI) – 40V, 600 mA Step Down COT Switching Regulator

November 1, 2007
LM34919
40V, 600 mA Step Down COT 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
■ ^{Integrated N-Channel buck switch}
■ ^{Integrated start-up regulator}
■ ^{Input Voltage Range: 8V to 40V}
■ ^{No loop compensation required}
■ ^{Ultra-Fast transient response}
■ ^{Operating frequency remains constant with load current}
and input voltage
■ ^{Maximum switching frequency: 1.6 MHz}
■ ^{Maximum Duty Cycle Limited During Start-Up}
■ ^{Adjustable output voltage}
■ ^{Valley Current Limit At 0.64A}
■ ^{Precision internal reference}
■ ^{Low bias current}
■ ^{Highly efficient operation}
■ ^{Thermal shutdown}
Typical Applications
■ ^{High Efficiency Point-Of-Load (POL) Regulator}
■ ^{Non-Isolated Telecommunication Buck Regulator}
■ ^{Secondary High Voltage Post Regulator}
Package
■ ^{micro SMD}
Basic Step Down Regulator
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