LM34930 Datasheet, PDF (1/18 Pages) National Semiconductor (TI) – Ultra Small 33V, 1A Constant On-Time Buck Switching Regulator with Intelligent Current Limit

June 23, 2008
LM34930
Ultra Small 33V, 1A Constant On-Time Buck Switching
Regulator with Intelligent Current Limit
General Description
The LM34930 constant On-Time Step Down Switching Reg-
ulator features all the functions needed to implement a low
cost, efficient, buck bias regulator capable of supplying in ex-
cess of 1A load current. This high voltage regulator contains
an N-Channel Buck Switch, and is available in a µSMD
bumped package. The constant on-time regulation principle
requires no loop compensation, results in fast load transient
response, and simplifies circuit implementation. The operat-
ing frequency remains constant with line and load. The valley
current limit results in a smooth transition from constant volt-
age to constant current mode when current limit is detected
without the use of current limit foldback. To reduce the pos-
sibility of saturating the inductor the valley current limit thresh-
old reduces as the input voltage increases, and the on-time
is reduced when current limit is detected. Additional features
include: Over-voltage indicator, Input over-voltage shutdown,
Vcc under-voltage lock-out, thermal shutdown, and maximum
duty cycle limiting.
Features
■ ^{Operating Input Voltage Range: 8V to 33V}
■ ^{Input over-voltage shutdown at 36V}
■ ^{Input absolute maximum rating of 44V}
■ ^{Integrated 1A N-Channel buck switch}
■ ^{Adjustable output voltage from 2.5V}
■ ^{Switching frequency adjustable to 2 MHz}
■ ^{Switching frequency remains nearly constant with load}
current and input voltage
■ ^{Ultra-fast transient response}
■ ^{No loop compensation required}
■ ^{Adjustable soft-start timing}
■ ^{Thermal shutdown}
■ ^{Precision 2% feedback reference}
■ ^{Input Over-Voltage indicator at 19V}
■ ^{Current limit scheme helps prevent inductor from}
saturation in load fault conditions
Package
■ ^{Micro SMD –12, 1.77 mm x 2.1 mm}
Typical Application, Basic Step-Down Regulator
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