LM34923 Datasheet, PDF (1/26 Pages) National Semiconductor (TI) – EVAL evaluation board provides the design engineer with a fully

LM34923
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SNVS695A – MARCH 2011 – REVISED FEBRUARY 2013
80-V 600-mA Constant On-Time Buck Switching Regulator
Check for Samples: LM34923
FEATURES
1
•2 Operating Input Voltage Range: 6V to 75V
• Integrated 80V, N-Channel Buck Switch
• Internal Start-up Regulator
• No Loop Compensation Required
• Ultra-Fast Transient Response
• Operating Frequency Remains Constant with
Line and Load Variations
• Adjustable Output voltage From 2.5V
• Precision Internal Reference, ±2.5%
• Intelligent Current Limit Reduces Foldback
• Programmable Input UV Detector with Status
Flag Output
• Pre-charge Switch Enables Bootstrap Gate
Drive with No Load
• Thermal Shutdown
• 10-Pin VSSOP Package
DESCRIPTION
The LM34923 Step Down Switching Regulator
features all of the functions needed to implement a
low cost, efficient Buck bias regulator. This high
voltage regulator contains an 80V N-Channel
MOSFET Switch and a startup regulator. The device
is easy to implement and is provided in an 10-pin
VSSOP package. The regulator’s control scheme
uses an on-time inversely proportional to V_IN. This
feature results in the operating frequency remaining
relatively constant with line and load variations. The
control scheme requires no loop compensation,
resulting in fast transient response. An intelligent
current limit is implemented with a forced off-time
which is inversely proportional to V_OUT. This scheme
ensures short circuit control while providing minimum
foldback. Other features include: Thermal Shutdown,
VCC Under Voltage Lock-out, Max Duty Cycle
Limiter, a Pre-charge Switch, and a programmable
Under Voltage Detector with a status flag output.
APPLICATIONS
• Non-Isolated Telecommunication Buck
Regulator
• Secondary High Voltage Post Regulator
• +42V Automotive Systems
Typical Application, Basic Step-Down Regulator
6V - 75V
Input
V_IN
VIN
GND
C1
R_T
VCC
LM34923
BST
SHUTDOWN
R_UV2
R_UV1
RT/SD
UV
R_UVO
UV STATUS
UVO
SW
FB
RTN
C3
C4
L1
D1
R_FB2
R_FB1
V_OUT
R3
C2
GND
1
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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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