Texas Instruments Incorporated (TI) 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 integrated circuit plus inductor. The devices feature an input voltage of 3 V to 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 the liquid crystal display (LCD) main display in today's clamshell phones.
TI's TPS61140 device allows a portable 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 TPS61140'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 maximize output current. Applying an external PWM signal to the select pin reduces the output current, thereby allowing white LED dimming.
High-Efficiency White LED Backlighting
TI's new TPS61150 high-frequency boost converter with two regulated current outputs drives white LEDs in LCD backlights for the sub and main displays in clamshell phones. As with the TPS61140, 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 of the white LEDs. The TPS61150 regulator's 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, while maintaining a high degree of efficiency and design flexibility. 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.
Key Features of the TPS61140 and TPS61150:
- 3 V to 6 V Input Voltage Range
- Two Outputs Each up to 27 V
- 0.7 A Integrated Switch
- Built-in Power Diode
- 1.2-MHz PWM for white LED Driver
- PFM for OLED Supply
- Up to 82 Percent Efficiency
- Up to 30-kHz PWM Dimming Frequency
- Individually Programmable Output
- Input to Output Isolation
- Overvoltage and Short-Circuit Protection
- Internal Over-Temperature Protection
- Undervoltage Protection
