Industry's First High-Current LED Driver that Enables Dual LED Operation

National Semiconductor Corp. today introduced the industry's first high-current light-emitting diode (LED) driver that enables dual LED operation for the camera flash function in portable multimedia devices. The LM3553, a member of National's PowerWise(R) energy-efficient product family, drives one or two high-current LEDs in series in handheld devices such as mobile phones, personal digital assistants (PDAs), smartphones, portable scanners and medical strobe lights.

National's LM3553 flash LED driver is a fixed-frequency, step-up DC-DC converter with two regulated current sinks, driving loads up to 1.2A from a single-cell Li-Ion battery. Using the driver's adjustable over-voltage protection circuitry allows designers to drive two high-current LEDs in a series configuration, which maximizes the illumination-to-power ratio. The LM3553 can drive the camera in a high-power flash mode for still photography or a low-power torch mode for video recording. To configure the driver to fit their application, designers can use the adjustable 128-flash current levels and 16-flash timer durations via an I2C compatible interface. The LM3553 also features built-in time-out protection to protect the flash LEDs in case of an error condition.

National's LM3553 flash LED driver maximizes the light output for low-power systems with peak efficiency equal to or greater than 90 percent, positioning it among National's PowerWise(R) family of energy-efficient products.

Technical Features of National's LM3553 LED Driver

National's LM3553 features an adjustable switch current limit for the use of small inductors with lower saturation currents. The voltage mode offers a 5V rail for backlight LEDs and audio amplifiers. One or more high-current LEDs can be driven either in a high-power flash mode or a lower-power torch mode controlled by either an internal register or the FEN and TX pins. The TX input forces the flash pulse into a low-current torch mode, allowing for synchronization to RF power amplifier events or other high-current conditions. A GPIO pin adds a hardware resource to the system. The hardware reset pin offers full control over the device in case of system failures. Additional features include internal soft-start to eliminate large in-rush currents during start-up and fast switching frequency, allowing for the use of smaller external components.

The LM3553 is offered in a 12-pin LLP(R) package. For more information on the LM3553 or to order samples or an evaluation board, visit

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