Power Electronics / Power Management


Dual-output boost converters for OLED and white LED displays

31 May 2006 Power Electronics / Power Management

Texas Instruments has introduced two new high-efficiency, dual-output DC-DC boost converters that can manage two sets of six white light-emitting diodes (LEDs) - all from a single IC with an inductor.

These devices feature an input voltage of 3-6 V and can deliver up to 0,7 A of output current, making them well suited to drive organic LED (OLED) sub-displays and white LED backlighting for LCDs such as those in today's clamshell phones.

TI's TPS61140 device allows an electronics designer to program each individual voltage and current level through external resistors. For additional flexibility, the designer can use each output's dedicated selection pin to turn them on separately or simultaneously. If the chip's voltage output is enabled, the boost converter is controlled by pulse frequency modulation (PFM) to achieve high efficiency over a wide load range. If the current output is selected, the device adopts a 1,2 MHz pulse width modulation (PWM) control method to maximise output current. Applying an external PWM signal to the 'select' pin reduces the output current, allowing white LED dimming.

TI's TPS61150 has two regulated current outputs to drive white LEDs in the backlights for the sub and main LCD displays in clamshell phones. This device's output current can be reduced by implementing a PWM signal on the select pins or an analog voltage on the ISET pin, resulting in PWM dimming. Its 1,2 MHz fixed switching frequency reduces output ripple and avoids audible noises associated with PFM control. The device's two outputs can also drive display and keypad backlights, together driving up to 12 white LEDs in one large display.

The TPS61140 and TPS61150 eliminate the need for any external active power components. The devices incorporate a power MOSFET and power diode. In addition, the high switching frequency reduces the size requirements of the external inductor and capacitor. They come in 10 pin, 3 x 3 mm QFN packaging.

For more information contact Rodney Farrow, Arrow Altech Distribution, +27 (0)11 923 9600, [email protected]



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