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Light manager tailored for smart phones

Posted: 20 Apr 2009 ?? ?Print Version ?Bookmark and Share

Keywords:light manager? unit light management? smart phone?

AAT2862 lighting management unit

Advanced Analogic Technologies Inc. (AnalogicTech) has developed the AAT2862 lighting management unit (LMU) that drives up to eight LEDs and integrates four low-dropout linear regulators (LDO).

Optimized for single-cell Li-ion/polymer powered systems, the AAT2862's capabilities are suitable for I?C-based high performance smart phones and other mobile devices that require the integration of two camera modules. The new LMU also adds an automatic fade-in/fade-out backlight control that simplifies design and reduces processor overhead.

"Given the complexity and diversity of feature sets found in today's cellphone product lines, designers can gain tremendous advantage in terms of design time and cost by using the same power management solution in multiple products," said Phil Dewsbury, product line director for AnalogicTech. "By delivering industry-standard I?C programmability across nine different LED combinations and I?C control across 16 different voltage settings for each LDO, the AAT2862 provides the level of versatility designers require to build complex products in short design cycles."

Improved efficiency
Operating from a 2.7V to 5.5V input voltage, the AAT2862 drives up to eight backlight LEDs at up to 30mA each. To ensure constant current over the entire battery range, the LEDs are driven from a tri-mode charge pump which automatically switches between 1x, 1.5x and 2x modes to maximize operating efficiency. The charge pump's high 1MHz operating frequency permits the use of small 1?F ceramic capacitors.

The eight LED outputs are programmable from 500?A up to 30mA. Two LED outputs can be programmed up to 60mA each. Current can be set to any of 32 separate levels via an industry-standard I?C interface. To ensure uniform display brightness, current matching is better than 3 percent. To balance power dissipation, high current matching exceeds 5 percent.

The new LMU also features three programmable automatic fade-in/fade-out times for backlight control. By implementing this function in hardware instead of software, processor overhead is reduced.

The AAT2862 also features four high performance low noise LDOs. The output of each LDO is programmable via the I?C serial interface to any of 16 voltages between 1.2V and 3.3V. Each regulator can supply up to 200mA load current. To support battery-operated applications, ground-pin current is limited to 80?A.

To ensure device integrity, the AAT2862 provides automatic soft start and built-in thermal protection.

The AAT2862 is qualified across the -40C to +85C temperature range. It is available in a Pb-free, 24-pin TQFN34 package. It sells for $1.81 in 1,000 quantities.

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