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Boost converters ease large-panel WLED design

Posted: 05 Feb 2007 ?? ?Print Version ?Bookmark and Share

Keywords:boost converters? WLED? lighting? AnalogicTech? LED?

AAT1235 and AAT1236 boost converters from AnalogicTech

AnalogicTech has rolled out two high-efficiency boost converters to address the design challenges in using multiple strings of series-connected white LEDs (WLEDs) to provide uniform illumination in large-panel lighting applications.

Many existing solutions rely on PWM techniques using a modulating DC input voltage that result in substantial flicker. AnalogicTech claims that with its AAT1235 and AAT1236 devices, designers can employ a single boost converter with a digital interface to run five 20mA strings of up to four series-connected WLEDs, and deliver a constant, non-pulsating forward current that ensure uniform brightness across the entire display, simultaneously reducing component count and simplifying design.

Large-format LCDs
Targeted at WLED applications for large-format LCD screens, the AAT1235 and AAT1236 boost converters offer a high-efficiency, high-voltage power source in a single package. Their five strings are split into two banks, one comprised of two current sinks for backlight applications and a second comprised of three current sinks for auxiliary lighting functions. Each bank of strings can be turned on or off independently or as a whole.

The two boost converters also promise designers substantial space savings. By integrating the driver and control line for multiple series-connected WLED strings into one circuit, the devices eliminate multiple discrete drivers, inductors, capacitors, resistors and diodes. Furthermore, by operating at 2MHz switching frequency, the devices also support the use of very small-footprint, 2.2?H inductors.

Operating from a 2.7-5.5V input, the AAT1235 and AAT1236 supply a maximum boost output of 24V at 100mA. The two backlight LED current sinks and the three output auxiliary lighting current sinks can be driven up to 30mA each using 16 user-programmable levels.

Automatic soft start
The AAT1235 features AnalogicTech's advanced simple serial control (AS?Cwire) serial digital control to turn on and off each output sink and adjust LED current by group. The AAT1236 boost converter offers the same features as the AAT1235, but with an I?C interface for configuration and control. Both devices also feature automatic soft start, overvoltage and over-temperature protection.

The AAT1235 and AAT1236 are specified across the -40 to 85C temperature range. They are available in a Pb-free, thermally enhanced, 16-pin TDFN34 packages.

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