Features Integrated N-Channel buck switch Integrated start-up regulator Input Voltage Range: 8V to 40V No loop compensation required Ultra-Fast transient response Operating frequency remains constant with load current and input voltage Maximum switching frequency: 2.0 MHz Maximum Duty Cycle Limited During Start-Up Adjustable output voltage Valley Current Limit At 0.64A Precision internal reference Low bias current Highly efficient operation Thermal shutdown Description The LM34919 Step Down Switching Regulator features all of the functions needed to implement a low cost, efficient, buck bias regulator capable of supplying 0.6A to the load. This buck regulator contains an N-Channel Buck Switch, and is available in a 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 lockout, thermal shutdown, gate drive under-voltage lockout, and maximum duty cycle limiter.

WEBENCH® LM34919     Min   Max   Range     VIN – V    8.00 – 40.00V     VOUT V    2.51 – 35.00V     IOUT A    ≤ 0.60A     Ambient Temp °C    ≤ 100°C   Footprint BOM Cost Efficiency What are WEBENCH® tools?

Typical Application *click for larger image	Block Diagram *click for larger image
Typical Performance *click for larger image

Parameters Values Output Current 600 mA Input Min Voltage 8 Volt Input Max Voltage 40 Volt Output Min 2.5 Volt Output Max 35 Volt Frequency Min Undefined kHz Frequency Max 1600 kHz Efficiency (peak) 90 % On/Off Pin Yes PowerGood / Error Flag No SoftStart Yes Sync Pin No Inverting Yes Flyback No RegType Switching Regulator Temperature Min -40 deg C Temperature Max 125 deg C Adjustable Output Yes Adj Switch Frequency Yes PWM Mode Constant on-time Topology Buck Special Features No compensation req'd; ultra fast transient response Step-Down Yes Multiple Output Capability No Output Power Undefined Watt Output Voltage Undefined Volt Output Range 2.5V to 35V Feedback Voltage 2.5 Volt Regulator Family Undefined Automotive Yes PowerWise Yes Synchronous Rectification No

Datasheets

Title		Size	Date	Other Language
	LM34919 Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator	377 Kbytes	2-Jun-08

Application Notes

Title		Size	Date	Other Language
	AN-1650: Application Note 1650 LM34919 Evaluation Board	338 Kbytes	8-Jun-07	中文

Other Technical Documents

Title		Type	Date
	Optimizing Ripple for a COT Buck Converter	External Article	2009-08-01

Part Number(s) (NSID)	Top View	Availability	Current Reported Stock	Budgetary Pricing	Pack Size
LM34919TL/NOPB RoHS Status	MICRO SMD	Full production Lead Time: 6 weeks	Distributor Region Qty ARROW Worldwide 485 DIGI-KEY Worldwide 356 MOUSER Worldwide 500 TAYLOR Americas 485	$1.20 each at 1K+ pcs	reel of 250
LM34919TLX/NOPB RoHS Status	MICRO SMD	Full production Lead Time: 6 weeks	Distributor Region Qty ARROW Worldwide 36000 DIGI-KEY Worldwide 0 MOUSER Worldwide 3000 TAYLOR Americas 36000	$1.20 each at 1K+ pcs	reel of 3000

All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

Moisture Sensitivity Level Data for LM34919.

A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

National's certificate of product compliance for LM34919 is located at RoHS Status.

Part Number(s) (NSID)	Description	Availability	Current Reported Stock	Budgetary Pricing	Pack Size
LM34919EVAL	Evaluation Board for the LM34919	Full production	Distributor Region Qty DIGI-KEY Worldwide 0 MOUSER Worldwide 2	$45.00 each	1
Description: The LM34919 evaluation board provides the design engineer with a fully functional buck regulator, employing the constant on time (COT) operating principle. This evaluation board provides a 5V output over an input range of 8V to 40V. The circuit delivers load currents to 600 mA, with current limit set at a nominal 700 mA. The board is populated with all components except R5, C9 and C10. These components provide options for managing the output ripple as described later in the LM34919 Application Note. Contents: LM34919 Evaluation Board LM34919 Datasheet Application Note 1650 for the LM34919 Evaluation Board

National Semiconductor follows the provisions of the Product Stewardship Guide for Customers (CSP-9-111C1) and Banned Substances and Materials of Interest Specification (CSP-9-111S2) for regulatory environmental compliance. Details may be found at: www.national.com/en/packaging/greennopb.html. Lead free products are RoHS compliant.

Lead Free product status is available through the search tool located here

Part Number(s) (NSID)	Weight (milligrams)	Type	Pins	MSL Rating	Peak Reflow	RoHS Status	CAD Symbols	Models	Package Marking Format
LM34919TL/NOPB	3.458	MICRO SMD	10	1	260	Detail	N/A	N/A	XYTT I SRYB
LM34919TLX/NOPB	3.458	MICRO SMD	10	1	260	Detail	N/A	N/A	XYTT I SRYB

All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

Moisture Sensitivity Level Data for LM34919.

A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

National's certificate of product compliance for LM34919 is located at RoHS Status.

Design Tools

Title	Size	Date
LM34919 Quick Start Calculator

CAD Symbols and Models N/A

Models N/A

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM34919TL	ABCD150	0	42680	0	0	6394000	1	1814314958
LM34919TLX	ABCD150	0	42680	0	0	6394000	1	1814314958

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

For more information on Reliability Metrics, please click here.

All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

Moisture Sensitivity Level Data for LM34919.

A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

National's certificate of product compliance for LM34919 is located at RoHS Status.