Features High-Voltage High-Side Current Source Allows for Grounded Cathode LED Operation Synchronous Boost Converter Peak Converter Efficiency >90% Accurate and Programmable LED Current ranging from 60 mA to 500 mA Adaptive LED Current Range Based on LED Configuration Dedicated Indicator Current Source Dedicated Torch and Strobe Pins Dual Mode Control (General Purpose or I 2C) Broken Inductor Detection Output Over-Voltage Protection Output and LED Short-Circuit Protection 400kHz I 2C-Compatible Interface 12-Bump, 1.575 mm x 2.1 mm x 0.6 mm micro SMD Package (TLA12BCA) Description The LM3555 is a 2 MHz fixed frequency, current mode synchronous boost converter designed to drive either a single flash LED at 500 mA or two series flash LEDs at 400 mA. A high-voltage current source allows the LEDs to be terminated to the GND plane eliminating the need for an additional return trace back to the IC. A dual mode control interface allows the user to configure the LM3555 with a general-purpose interface using two enable pins for control or an I 2C allowing a higher level of control. Both interfaces allow access to the indicator, assist light and flash modes. A dedicated Strobe pin provides a direct interface to trigger the flash event, while an external Torch pin provides an additional method for enabling the LEDs in a constant current mode. The LM3555 can adaptively scale the maximum flash level delivered to the LED/LEDs based upon the flash configuration, whether it be a single LED or two LEDs in series. Eight protection features are available on the LM3555 ranging from over-voltage protection to broken inductor detection. The LM3555 has four selectable inductor current limits to help the user select an inductor that is appropriate for the design. Applications Camera Phone LED Flash

typ app

Typical Application click for larger image typ app	Block Diagram click for larger image block diag
Typical Performance click for larger image 2 LED BRC 3.6V

Datasheets

Title		Size	Date	Other Language
	LM3555 Synchronous Boost Converter with 500 mA High Side LED Driver and Dual-Mode Control Interface	766 Kbytes	10-Nov-11

Part Number(s) (NSID)	Top View	Availability	Current Reported Stock	Budgetary Pricing	Pack Size
LM3555TLE/NOPB RoHS Status	MICRO SMD	Full production Lead Time: 6 weeks	Distributor Region Qty DIGI-KEY Worldwide 805 MOUSER Worldwide 297	$1.30 each at 1K+ pcs	reel of 250
LM3555TLX/NOPB RoHS Status	MICRO SMD	Full production Lead Time: 6 weeks	Distributor Region Qty DIGI-KEY Worldwide 0	$1.30 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 LM3555.

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 LM3555 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
LM3555TLE/NOPB	3.802	MICRO SMD	12	1	260	Detail	N/A	N/A	XYTT I 3555
LM3555TLX/NOPB	3.802	MICRO SMD	12	1	260	Detail	N/A	N/A	XYTT I 3555

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 LM3555.

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 LM3555 is located at RoHS Status.

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)
LM3555TLE	CMOS7	0	21301	0	0	1584000	3	449464325
LM3555TLX	CMOS7	0	21301	0	0	1584000	3	449464325

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 LM3555.

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 LM3555 is located at RoHS Status.