LM34919_08 Datasheet, PDF (1/18 Pages) National Semiconductor (TI) – Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator

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
■ ^{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: 2.0 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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