Features VIN Range: 2.7V-7.5V Small External Components 1.25 MHz Constant-Switching Frequency Output Over-Voltage Protection Input Under-Voltage Protection Cycle-By-Cycle Current Limit TRUE SHUTDOWN: No DC current paths to ground during shutdown Low Profile Package: <1 mm Height -8 Pin LLP No External Compensation Description The LM3557 is a complete solution for white LED drive applications. With minimal external component count, no DC current leakage paths to ground, cycle-by-cycle current limit protection, and output over-voltage protection circuitry, the LM3557 offer superior performance and cost savings over standard DC/DC boost component implementations. The LM3557 switches at a fixed-frequency of 1.25 MHz, which allows for the use of small external components. Also, the LM3557 has a wide input voltage range to take advantage of multi-cell input applications. With small external components, high fixed frequency operation, and wide input voltage range, the LM3557 is the most optimal choice for LED lighting applications. Applications White LED Display Lighting Cellular Phones PDAs

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

Datasheets

Title		Size	Date	Other Language
	LM3557 Step-Up Converter for White LED Applications	644 Kbytes	9-May-06

Part Number(s) (NSID)	Top View	Availability	Current Reported Stock	Budgetary Pricing	Pack Size
LM3557SD-2/NOPB LM3557SD-2 RoHS Status	LLP	Full production Lead Time: 6 weeks	Distributor Region Qty DIGI-KEY Worldwide 0 FARNELL Europe and Asia 931 MOUSER Worldwide 900 NEWARK Americas 812	$0.68 each at 1K+ pcs	reel of 1000
LM3557SDX-2/NOPB LM3557SDX-2 RoHS Status	LLP	Full production Lead Time: 6 weeks	Distributor Region Qty DIGI-KEY Worldwide 0	$0.68 each at 1K+ pcs	reel of 4500

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 LM3557.

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 LM3557 is located at RoHS Status.

Part Number(s) (NSID)	Weight (milligrams)	Type	Pins	MSL Rating	Peak Reflow	RoHS Status	CAD Symbols	Models	Package Marking Format
LM3557SD-2/NOPB LM3557SD-2	20.736 20.803	LLP	8	1 1	260 260	Detail	Download	N/A	ZXYTT L147B
LM3557SDX-2/NOPB LM3557SDX-2	20.736 20.803	LLP	8	1 1	260 260	Detail	Download	N/A	ZXYTT L147B

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 LM3557.

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 LM3557 is located at RoHS Status.

CAD Symbols and Models Download LM3557 CAD Symbols

Models N/A

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM3557SD-2	ABCD150	0	42680	0	0	6394000	1	1814314958
LM3557SDX-2	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 LM3557.

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 LM3557 is located at RoHS Status.