In large panel lighting applications, the use of multiple strings of series white LEDs (WLEDs) is not easy to achieve consistent illumination. Many existing solutions rely on pulse width modulation (PWM) techniques that utilize a modulated DC input voltage to cause picture flicker. In view of this, AnalogicTech has introduced AAT1235 and AAT1236 boost converters, allowing designers to implement 5 sets of 20mA of four series-connected WLEDs through a single boost converter with digital interface. It is connected in series and provides a fixed, non-fluctuating forward current that provides consistent brightness to the display while reducing component count and simplifying design.
AnalogicTech's AAT1235 and AAT1236 are designed for WLED applications with large LCD screens that provide high efficiency, high voltage power in a single package. The five series of this component are divided into two groups, one containing two current sinks for backlight applications and the second containing three current sinks for auxiliary illumination, each in series Independent or full off or on.
These two sets of boost converters allow designers to actually save board space by integrating control lines and drivers for multiple series WLEDs into a single circuit that eliminates the need for drivers, inductors, capacitors, resistors, and diodes. And because it can operate at a high switching frequency of 2MHz, it can use a 2.2 micro-Henry inductor with a very small footprint.
The AAT1235 and AAT1236 operate from a 2.7 to 5.5V input voltage and provide a maximum boost output voltage of up to 24V at 100mA. The two sets of backlight LED current sinking ends and three sets of output auxiliary lighting current sinking terminals, each group can provide up to 30 mA through 16 user-settable steps.
The AAT1235 turns off or turns on each output through AnalogicTech's AS2Cwire serial digital control and adjusts the LED current in groups. The AAT1236 boost converter offers the same functionality as the AAT1235, but with an I2C interface for configuration and control. Both components feature automatic soft start, over voltage and over temperature protection. The AAT1235 and AAT1236 are available in the -40 to +85°C temperature range and are available in lead-free, thermally rugged 16-pin TDFN34 packages.
Source: Electronic Engineering 