LM34917A_15 Datasheet, PDF (1/22 Pages) Texas Instruments – Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with Intelligent Current Limit

LM34917A
www.ti.com
SNOSAX7D – DECEMBER 2007 – REVISED MARCH 2013
LM34917A Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with
Intelligent Current Limit
Check for Samples: LM34917A
FEATURES
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•2 Functional Input Voltage Range: 8V to 33V
• DSBGA package
• Input Over-Voltage Shutdown at ≊35V
• Transient Capability to 50V
• Integrated N-Channel buck switch
• Valley current limit varies with V_IN and V_OUT to
reduce excessive inductor current
• On-time is reduced when in current limit
• Integrated start-up regulator
• No loop compensation required
• Ultra-Fast transient response
• Maximum switching frequency: 2 MHz
• Operating frequency remains nearly constant
with load current and input voltage variations
• Programmable soft-start
• Precision internal reference
• Adjustable output voltage
• Thermal shutdown
TYPICAL APPLICATIONS
• High Efficiency Point-Of-Load (POL) Regulator
• Non-Isolated Buck Regulator
• Secondary High Voltage Post Regulator
PACKAGE
• 12-Bump DSBGA Package
DESCRIPTION
The LM34917A Step-Down Switching Regulator
features all the functions needed to implement a low
cost, efficient, buck bias regulator capable of
supplying at least 1.25A to the load. To reduce
excessive switch current due to the possibility of a
saturating inductor the valley current limit threshold
changes with input and output voltages, and the on-
time is reduced when current limit is detected. This
buck regulator contains an N-Channel Buck Switch,
and is available in the 12 pin DSBGA package. The
constant on-time feedback regulation scheme
requires no loop compensation, results in fast load
transient response, and simplifies circuit
implementation. 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 results in a
smooth transition from constant voltage to constant
current mode when current limit is detected, reducing
the frequency and output voltage, without the use of
foldback. Additional features include: V_CC under-
voltage lock-out, input over-voltage shutdown,
thermal shutdown, gate drive under-voltage lock-out,
and maximum duty cycle limit.
Basic Step Down Regulator
8V - 33V
Input
C1
SHUT
DOWN
VIN
VCC
LM34917A
R_ON
BST
RON/SD
SW
SS
C6
RTN
ISEN
FB
SGND
C3
L1
C4
D1
R3
C8
R1
C7
R2
V_OUT
C2
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2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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