Analog Devices, Inc., an integrated circuit developer specializing in power management for communications, computing and consumer electronics devices, announced the addition of two new members to its growing portfolio of high-current white light-emitting diode (WLED) flash drivers. The dual-channel boost converters, numbered AAT1271 and AAT1272, support two WLEDs at up to 750mA or one WLED with up to 1.5A, and they are available in a compact 3x3-mmTDFN package. They are the first of its kind on the line of Analogic WLED drivers, with the proprietary AS2Cwire interface and industry-standard I2C interface. The extra processing power of these two buses provides designers with great flexibility in adjusting the drive current to change the brightness of the WLED. At the same time, the boost converter's high drive current and small 3x3-mm footprint provide a highly attractive new alternative to bulky xenon solutions.
“Today, many digital cameras and cell phone cameras compensate for ambient light deviations to maximize picture quality,†explains PhilDewsbury, product line director of Analogic Lighting, “AAT1271 and AAT1272 through additional control capabilities using AS2Cwire and I2C buses. Allows designers to freely change the brightness of the flash and the brightness of the movie mode at multiple levels to improve picture quality."
Both the AAT1271 and AAT1272 are high efficiency, high current boost converters designed for LED photoflash applications. Designed for single-cell Li-Ion batteries that power mobile systems, these new devices operate from an input voltage range of 2.7V to 5.5V. Both converters use a switching frequency of up to 2MHz to help reduce system footprint by allowing the use of smaller external inductors and capacitors. They achieve up to 85% efficiency with a 1μH inductor.
The AAT1271 and AAT1272 are dual-channel capable of driving two high-current WLEDs at up to 750mA each. In addition, the two channels can also be combined to drive a WLED with a current of up to 1.5A. The AAT1271 comes with Analogic's proprietary single-wire AS2C interface, while the AAT1272 provides an industry-standard two-wire I2C interface.
Both converters offer separate flash start and movie mode start input modes to control flash and movie mode operation. Designers used a single external resistor to set the full-scale flash LED current and provide a 7.3:1 current ratio preset from flash to film mode. Designers use the AS2Cwire or I2C interface to adjust the film mode current from a preset value to any other 15 levels. In addition, the AAT1271 adds a flash suppression input that can be used in GSM mobile applications to reduce flash current in power amplifier (PA) transmissions, thereby avoiding system restarts caused by excessive battery drain under high battery current conditions.
Due to their high drive current capability, both converters have an input current limit and a true load disconnect switch that reduces the supply current at shutdown to less than 1μA.
The two new converters also include a user-programmable flash safety timer. This feature can be used to protect the flash LED from thermal damage in the event of software failure by terminating the flash pulse without regard to the signal conditions of the flash activation. With the AS2C or I2C bus, the safety timer can be programmed on 16 different levels.
Price and availability
The AAT1271 and AAT1272 are rated for operation over the -40oC to +85oC and are available in a 3x3-mm, 14-pin TDFN package. The AAT1271 and AAT1272 are priced at $1.49 each in 1,000-piece quantities.
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