Highly Flexible Converters Allow On-the-Fly Output Current Correction to Enhance Photo Quality
"Many digital still cameras and phone cameras today maximize photo quality by compensating for ambient light deviations," explains Phil Dewsbury, Product Line Director for Lighting Products at AnalogicTech. "By taking advantage of the additional control capabilities in the AS(2)Cwire and I(2)C bus, the AAT1271 and AAT1272 allow designers to modify flash brightness or movie mode brightness on-the-fly across multiple levels and thereby improve picture quality."
Increased Current Control
Both the AAT1271 and AAT1272 are high efficiency, high current boost converters designed for LED photo flash applications. Operating off a 2.7V to 5.5V input voltage range, the two new devices are targeted at single-cell Lithium-ion battery powered mobile systems. Both converters use a high 2 MHz switching frequency which helps reduce system footprint by allowing the use of smaller external inductors and capacitors. The two new converters can achieve up to 85% efficiency with 1uH inductors.
The AAT1271 and AAT1272 feature two channels capable of driving two high current WLEDs at up to 750mA each. Alternately, the two channels can be combined to drive a single WLED at up to 1.5A. The AAT1271 features AnalogicTech's proprietary single-wire AS(2)C interface, while the AAT1272 offers the industry-standard two-wire I(2)C interface.
Both converters supply separate flash enable and movie-mode enable inputs to control flash and movie-mode operation. Designers use a single, external resistor to set full-scale flash LED current. A default 7.3:1 flash-to-movie-mode current ratio is provided. Designers can adjust the movie-mode current level from the default setting to any of 15 other levels using either the AS(2)Cwire or I(2)C interface. The AAT1271 also adds a flash inhibit input that can be used in GSM mobile applications to reduce the flash current during PA transmission to avoid a system reset due to excessive battery droop in high battery current conditions.
Given their high drive current capability, both converters also feature input current limit capability and a true load disconnect switch that reduces supply current in shutdown to < 1uA.
The new converters also include a user-programmable flash safety timer. This function can be used to protect the flash LEDs from thermal damage in the event of a software failure by terminating the flash pulse regardless of the FL enable signal condition. Using the AS(2)C or I(2)C bus, the safety timer can be programmed across 16 different levels.
Price and Availability
Both devices are qualified across the -40 degrees C to +85 degrees C temperature range and come in a 3x3-mm 14-pin TDFN package. The AAT1271 and the AAT1272 sell for $1.49 in 1K quantities.
Advanced Analogic Technologies, Inc. (AnalogicTech) is a supplier of Total Power Management(TM) semiconductor solutions for mobile consumer electronic devices, such as wireless handsets, notebook and tablet computers, smartphones, digital cameras, wireless LAN, and personal media players. The company focuses its design and marketing efforts on the application-specific power management needs of consumer, communications, and computing applications in these rapidly evolving devices. AnalogicTech also develops and licenses device, process, package, and application-related technology. AnalogicTech is headquartered in Santa Clara, California and Macau, S.A.R., with offices in China (Beijing, Shanghai and Shenzhen), Hong Kong, Taiwan, Japan, South Korea, Sweden, France and United Kingdom, as well as a worldwide network of sales representatives and distributors. The company is listed on the NASDAQ exchange under the ticker symbol AATI. For more information, please visit the AnalogicTech website: http://www.analogictech.com. (AnalogicTech - G)
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