National Semiconductor unveiled what it claims is the industry's first high-current LED driver that enables dual LED operation for the camera flash function in portable multimedia devices. The LM3553 drives either 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.
The LM3553 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. The adjustable over-voltage protection circuitry allows designers to drive two high-current LEDs in a series configuration, maximizing the illumination-to-power ratio. It 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.
National's 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 family of energy-efficient products.
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.
Available now, the LM3553 is priced at $1.20 each in 1,000-unit quantities. The LM3553 is offered in a 12-pin LLP package. For more information or to order samples or an evaluation board, visit: National Semiconductor.
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