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Boost converters offer 'smallest possible inductor-based solution'

Posted: 15 Dec 2004 ?? ?Print Version ?Bookmark and Share

Keywords:texas instruments? ti? synchronous boost converter? light emitting diode? led?

Texas Instruments Inc. (TI) announced a family of synchronous boost converters that can power up to five series white light emitting diodes (LEDs).

Measuring 1.5-by-1.5mm, the new ICs allow portable designers to implement the smallest possible inductor-based solution to efficiently power and control white LED backlights in smart phones, PDAs, digital still cameras and other handheld electronics, said TI.

The TPS6106x family of specialized dc-dc converters support input voltages from 2.7V to 6V, and can power up to three-, four- and five-series LEDs. According to the press release, the products' tiny chip scale package and minimum number of required external components enable a power supply circuit solution smaller than many non-inductor based, charge pump solutions. The TPS61060, TPS61061 and TPS61062 chips integrate a 400mA power MOSFET and synchronous rectifier, eliminating the need for an external series Schottky diode. Additionally, the 1MHz fixed switching frequency allows the converters to work with smaller, low-value external components, such as a 10?H inductor and a 220nF output capacitor.

An external current sense resistor sets the regulated LED current. A dedicated input in the TPS6106x devices enables simple, wide-range digital brightness control using a host microcontroller's general purpose input/output pin. The digital dimming technique allows step adjustment of the feedback reference voltage to the regulator. Alternatively, LED brightness can be controlled by applying a pulse-width modulation (PWM) signal to the chip enable pin, or by introducing an analog signal to the feedback input.

For safety and protection, the TPS6106x features integrated over-voltage, and short circuit sensing and thermal shutdown. Each device has a different over-voltage protection threshold (14V, 18V and 22.75V) corresponding to the maximum number of series LEDs. The internal MOSFETs are turned off when the converters are disabled to prevent current leakage into the LEDs and conserve battery power. In shutdown, these parts consume <3?A.

The TPS61060, TPS61061 and TPS61062 are already available in volume quantities. Each device is housed in an 8-pin, QFN or 8-pin, chip scale package. Suggested resale pricing in quantities of 1,000 is $1.35 for the TPS61060, $1.40 for the TPS61061 and $1.45 for the TPS61062. Evaluation modules, white LED application notes and the company's Power Management Selection Guide are available online.

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