LM34923_14 Datasheet, PDF (1/26 Pages) Texas Instruments – 80V, 600 mA Constant On-Time Buck Switching Regulator

LM34923
www.ti.com
SNVS695 – MARCH 2011
LM34923 80V, 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
TYPICAL APPLICATIONS
• Non-Isolated Telecommunication Buck
Regulator
• Secondary High Voltage Post Regulator
• +42V Automotive Systems
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 MSOP-10 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.
Package
• MSOP - 10
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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Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
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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.
Copyright © 2011, Texas Instruments Incorporated