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LM34917A Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with Intelligent Current Limit from the PowerWise® Family


source: | post time:2010-04-29

Part Number(s)
(NSID)
Top View Type Pins MSL Rating Peak Reflow RoHS
Status
CAD Symbols Models Package
Marking
Format
LM34917ATL/NOPB
MICRO SMD 12 1 260 Detail Download N/A
XYTT
I SRHA
LM34917ATLX/NOPB
MICRO SMD 12 1 260 Detail Download N/A
XYTT
I SRHA

PDFClick link to Download

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: VCC under-voltage lock-out, input over-voltage shutdown, thermal shutdown, gate drive under-voltage lock-out, and maximum duty cycle limit.

Features

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 VIN and VOUT 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

Diagrams

Typical Application
*click for larger image

LM34917A Basic Step Down Regulator

 

 

 

Block Diagram
*click for larger image

LM34917A Typical Application and Block Diagram

 


Typical Performance
*click for larger image


 


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Next:LM34919 Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator from the PowerWise® Family


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