Features • Up to 5A Flash Current • 4 Selectable Super-Capacitor Charge Voltage Levels (4.5V, 5.0V, 5.3V, Optimized) • Flash Optimized Charge Mode for Optimal Efficiency • -33% Faster Charge Time Using Optimal Mode • -49% Less Power Dissipated in Current Source using Optimal Charge Mode • Fast Super-Capacitor Charger with 500 mA Input Current Limit • Adjustable Torch Current (60mA to 200mA) • Ambient Light or LED Thermal Sensing with Current Scaleback • End-of-Charge Output ( ^EOC) • Dedicated Indicator LED Current Source • No Inductor Required • Manual Flash Enable via Strobe Pin Input • Programmable Flash Pulse Duration, and Torch and Flash Currents via I 2C Compatible Interface • True Shutdown (LED Disconnect) • Flash Time-Out Protection • LED Temperature Protection or Ambient Light Sensing Pin • Low Profile 20–Pin LLP Package (3.0 mm × 2.5 mm × 0.8 mm) Description LM3550 is a low noise, switched capacitor DC/DC converter designed to operate as a current-limited and adjustable (up to 5.3V) super-capacitor charger. LM3550 features user selectable super-capacitor charge termination voltages and an optimal charge termination mode that maximizes flash energy efficiency by accounting for flash element losses. Additionally, the device provides one adjustable constant-current output (up to 200mA) and one NFET controller ideal for driving one or more high current LEDs either in a high power Flash mode or a low power Torch mode. The LM3550 can be configured to utilize a proprietary super-capacitor charging scheme (Optimal Mode), allowing faster charging times (0 to Target Voltage) and lower current source power dissipation. Optimal Charge mode adapts to changes in the flash LEDs forward voltage as well as the super-capacitor's ESR ensuring that the super-capacitor is charged to the ideal voltage required to sustain constant current flash operation. The LED current and Flash pulse duration of the LM3550 can be programmed via an I 2C compatible interface. The Strobe pin allows the Flash to be toggled via a Flash enable signal from a camera module. The ^EOC pin sinks current when the output voltage reaches 95% of the final value. The ALD/TEMP input pin allows either a light sensor to adjust the flash current level based on the ambient light conditions, or it allows for over-temperature detection and protection of the LED during high power operation or high ambient temperature conditions by connecting an NTC thermistor temperature monitoring circuit to the pin. Notice: This document is not a full datasheet. For more information regarding this product or to order samples, please contact your local National Semiconductor sales office or visit http//www.national.com/support/dtr.html. Applications • Camera Phones • Digital Still Camera • Voltage Rail Management

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Datasheet

Title		Size	Date	Other Language
	LM3550 PRODUCT BRIEF 5A Flash LED Driver with Automatic Vf and ESR Detection for Mobile Camera Systems	128 Kbytes	1-May-09

Featured Application Notes

Title		Size	Date	Other Language
	AN-1823: Application Note 1823 LM3528 Evaluation Board	869 Kbytes	4-Aug-08

More Application Notes

Title		Size	Date	Other Language
	AN-1495: Application Note 1495 LM3552 White LED Flash Driver Evaluation Board	626 Kbytes	27-Sep-06	中文
	AN-1780: Application Note 1780 LM3553 1.2A Dual Flash LED Driver System with I2C Compatible Interface	1427 Kbytes	12-Mar-08

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM3550SP	CMOS7	0	18406	0	0	1089000	4	309006723
LM3550SPX	CMOS7	0	18406	0	0	1089000	4	309006723

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.

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