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Inductorless, dual output LED flash drivers introduced

Posted: 05 Jun 2008 ?? ?Print Version ?Bookmark and Share

Keywords:dual output LED flash drivers? LED flash/lamp driver ICs? GPIO interface?

Leadis Technology Inc. has started sampling the LDS8620 and the LDS8621, a new family of inductorless 200mA, dual-output LED flash/lamp drivers, in low-profile (0.8mm), space-saving 3mm x 3mm TQFN packages.

"With the LDS8620 and the LDS8621, Leadis continues to expand its charge-pump-based product portfolio by addressing fast-growing markets in portable LED lighting applications," said Adolfo Garcia, senior director of LED drivers for Leadis Technology. "Some examples of portable lighting applications include LED flashlights, flash/lamp LEDs in video and camera cellphones, PDAs, smart phones and digital cameras."

Consistent with providing high-quality, cost-effective solutions for the market, Leadis has joined with Seoul Semiconductor, a recognized developer and market leader of high-current, high-brightness white and RGB LEDs. "We enthusiastically recommend that our customers use Seoul Semiconductor's flash LEDs, especially the FCW301Z (in single flash LED applications) with our LDS8620 or the LDS8621," Garcia continued. "The multimode architecture of the LDS8620/21's inductorless boost converter with their LED's low and stable forward LED voltage and its high luminous intensity combine to produce a very high-performance, high-efficiency solution."

"We are pleased that Leadis has chosen to recommend our flash LEDs, especially the FCW301Z, with their LDS8620 and LDS8621 LED flash/lamp driver ICs. Leadis is proving to be a valuable partner with innovative LED driver solutions to compliment our high-current, high-brightness LEDs," said Daniel Park, PR manager of Seoul Semiconductor.

The LDS8620 and the LDS8621 are optimized for portable lighting applications powered by Li-ion and polymer batteries. They also operate very efficiently from single Li/MnO2 batteries, from three AA dry cell batteries, and from fixed power supplies up to 5.5V. To achieve up to 95 percent efficient operation, both products implement a multi-mode boost converter that automatically switches from 1x to 1.33x to 1.5x to 2x to maintain regulated LED current, in torch or full-flash mode. External component count is kept to a minimum (two, low-cost 0.22?F switching capacitors and two, 1?F bypass capacitors) because LED flash current is factory preset to 96mA per output. The LDS8620 and the LDS8621 also incorporate Leadis' proprietary, ultra low voltage dropout PowerLite Current Regulator (PCR) technology, which allows the inductorless boost converter to remain in 1x operating mode longer, extending battery runtime.

Production availability of the LDS8620 and the LDS8621 is scheduled for Q3 08.

More details
To configure one or both LED[A/B] outputs and to set the LED current for torch (or movie-mode) or full-flash operation, the LDS8620's logic interface at its EN/SET pin implements an industry-common, single-wire protocol. Its internal current control register is 6 bits deep, providing a 1.5mA LED current resolution from 0.5mA to 96mA. Single-wire LED configuration/control interface is very useful in flip-style cellphones where the high current LED and the LED driver are found on opposite sides of a cellphone's hinge.

The LDS8621 is parametrically identical to the LDS8620 except that its output configuration and LED current are controlled through a two-wire, dual-role logic interface. Its logic interface functions as both an IC enable and a PWM-mode flash LED brightness control. Its PWM1 input pin controls the operation of the LEDA output as its PWM2 input pin controls the operation of the LEDB output. Both PWM1 and PWM2 input signals can be controlled independently or connected together and driven by an application/baseband processor's GPIO interface.

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