Product category:
Power Supply ICs and Controllers
News Release from: Advanced Analogic Technologies | Subject: AAT1282
Edited by the Electronicstalk Editorial
Team on 30 May 2008
Boost convertor powers up camera flashes
Device uses a supercapacitor to deliver the high peak current needed to support the high intensity flash required for mobile phones.
Several LED vendors have announced products that approach the light intensity of a conventional xenon flash, the de facto yet bulky standard in today's high-resolution digital still cameras or smartphones But the adoption of LED flash in portable applications has been limited due to the high levels of battery current, forward voltage and peak current required to produce this intensity
This article was originally published on Electronicstalk on 19 Sep 2008 at 8.00am (UK)
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By storing the output of a boost convertor in a high-capacity supercapacitor, AnalogicTech's AAT1282 allows designers to use WLEDs to deliver the high-intensity light needed for flash and video applications in high megapixel cameras without draining or damaging the battery.
The AAT1282 is the industry's first 2A flash LED driver IC capable of delivering high intensity light from white LEDs (WLEDs).
Combining a high frequency boost convertor with fixed input current limiting, dual output regulated current sinks and I2C control, the device uses a supercapacitor to deliver the high peak current needed to support the high intensity flash required for mobile phones featuring cameras with resolutions of 5Mpixel and higher while protecting the battery.
Further reading
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Family offers designers of LAN equipment operating off a low-cost 12V adapter an ideal opportunity to boost efficiency and reduce product footprint.
Two convertors in one boost efficiency
Devices combine two buck convertors with a low input voltage used to post-regulate the second buck convertor.
Power IC sports two convertors and four LDOs
The highly integrated AAT2603 comes in a small 4 x 4mm TDFN package.
Operating across a 2.7 to 5.5V input, the AAT1282 is designed for LED photo flash applications in a variety of single-cell Li-ion powered products.
The high efficiency, high current step-up convertor features two output current sinks each providing a regulated 1A current.
The two LED current sources share the output current equally.
They can be connected together to apply full 2A output current into a single white LED or each diode can be connected to its corresponding current source and the driver can provide two independently-controlled 1A outputs.
Designed specifically to charge a supercapacitor, the step-up convertor features an integrated fixed input current limiter to limit the battery current and to avoid large voltage drops that can cause the phone to reset.
Current limit is set at 800mA for the AAT1282, but other values can be requested.
The step-up convertor also helps minimise end product footprint by operating at a high 2MHz switching frequency that allows the use of a compact 1uH inductor and 2.2uF output capacitor.
"The AAT1282 is a supercapacitor-optimised LED flash driver that allows device designers to harness supercapacitor power-boosts into high-resolution WLED flash units that far outshine standard battery-powered ones and rival xenon flash units", said Pierre Mars, Vice President of Applications Engineering for thin-form-supercapacitor-pioneer Cap-XX.
"The AAT1282 driver integrates all of the circuitry required to charge the supercapacitor, manage inrush current, and control LED current, thus saving development time, board space, and component cost".
The WLED driver uses an industry-standard I2C serial digital input to enable, disable and set the movie-mode (torch) current for each flash LED across 16 levels.
The I2C interface is also used to set flash/movie-mode current ratio, output channel control and safety timer.
Maximum flash and movie-mode current is set by a single external resistor.
The ratio between flash and movie-mode current is preset at 7.3:1 but can be adjusted to a wide range of other values.
An independent flash enable is provided to initiate the flash operation and to control a default timer that can be used to terminate a flash event at the end of a user-programmed delay or as a safety feature to prevent the LED from over-dissipating in the event of a software failure.
The AAT1282 also features a true load disconnect function that isolates the load from the power source while in the off or disabled state.
By guaranteeing less than 1.0uA shutdown current, this feature essentially eliminates leakage current.
To protect the device in the event of an output short-circuit condition, the driver IC also features an integrated thermal management system.
Built-in circuitry prevents excessive inrush current during startup.
The AAT1282 is qualified across the -40 to +85C temperature range.
It is available in a 14-pin 3 x 3mm TDFN package.
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