Product category: Power Supply ICs and Controllers
News Release from: National Semiconductor | Subject: LM3553
Edited by the Electronicstalk Editorial Team on 03 April 2008
LED driver doubles handset flashes
Device drives one or two high-current LEDs in series in handheld devices such as mobile phones, PDAs, smartphones, portable scanners and medical strobe lights.
National Semiconductor Corp has 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 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
This article was originally published on Electronicstalk on 5 Jan 2001 at 8.00am (UK)
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National's LM3553 flash LED driver is a fixed-frequency, step-up DC/DC convertor with two regulated current sinks, driving loads up to 1.2A from a single-cell Li-ion battery.
Using the driver's adjustable overvoltage protection circuitry allows designers to drive two high-current LEDs in a series configuration, which maximises 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 maximises the light output for low-power systems with peak efficiency of at least 90%, 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 synchronisation 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 package, priced at US $1.20 each in 1000-unit quantities.
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