Datasheet

UVLO
VIN
VCC
SW Pin
Inductor
Current
SS Pin
t2
V
OUT
7.0V
2.5V
t1
LM34919B
LM34919B-Q1
www.ti.com SNVS623A –MAY 2010–REVISED FEBRUARY 2013
Figure 25. Start Up Sequence
FUNCTIONAL DESCRIPTION
The LM34919B Step Down Switching Regulator features all the functions needed to implement a low cost,
efficient buck bias power converter capable of supplying at least 0.6A to the load. This high voltage regulator
contains an N-Channel buck switch, is easy to implement, and is available in a DSBGA package. The regulator’s
operation is based on a constant on-time control scheme, where the on-time is determined by V
IN
. This feature
allows the operating frequency to remain relatively constant with load and input voltage variations. The feedback
control requires no loop compensation resulting in very fast load transient response. The valley current limit
detection circuit, internally set at 0.64A, holds the buck switch off until the high current level subsides. This
scheme protects against excessively high current if the output is short-circuited when V
IN
is high.
The LM34919B can be applied in numerous applications to efficiently regulate down higher voltages. Additional
features include: Thermal shutdown, V
CC
under-voltage lockout, gate drive under-voltage lockout, and maximum
duty cycle limiter.
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