Datasheet

UVLO
VIN
VCC
SW Pin
Inductor
Current
SS Pin
t2
V
OUT
7.0V
2.5V
t1
LM34919
www.ti.com SNOSAY2E –MAY 2007–REVISED FEBRUARY 2013
Figure 11. Start Up Sequence
FUNCTIONAL DESCRIPTION
The LM34919 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 LM34919 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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