LM34917A_14 Datasheet, PDF (1/21 Pages) Texas Instruments – Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with Intelligent Current Limit

LM34917A
www.ti.com
SNOSAX7C – DECEMBER 2007 – REVISED MAY 2008
LM34917A Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with
Intelligent Current Limit
Check for Samples: LM34917A
FEATURES
1
•2 Functional Input Voltage Range: 8V to 33V
• Micro SMD 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
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 micro SMD 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.
Package
• micro SMD Package
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
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 © 2007–2008, Texas Instruments Incorporated