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White LED driver integrates Class AB audio amplifier

Posted: 19 Jun 2007 ?? ?Print Version ?Bookmark and Share

Keywords:white LED driver? LED? Class AB audio amplifier?

Maxim Integrated Products unveils the MAX8678, the industry's only white LED (WLED) driver to combine a highly efficient negative charge pump with a fully differential, bridged audio amplifier. Available in a tiny, 3-by-3-by-0.8mm, TQFN package, this single-chip solution is 50 percent smaller than the standard two-chip solution.

To achieve the industry's highest efficiency, MAX8678 features a negative architecture that completely eliminates high-side in-line resistance, delaying 1x to 2x mode transition during battery discharge. The independent adaptive-mode switching for each LED further extends battery life, even with large LED forward-voltage mismatch. These innovative features enable the MAX8678 to be 12 percent more efficient than competing solutions, thus making it ideal for use in cellphones, smartphones, PDAs and other handheld devices in which space and battery life are critical.

MAX8678 is claimed to be the only WLED driver to seamlessly integrate a mono, Class AB audio amplifier. This audio amplifier accepts differential input signals and offers excellent noise immunity to improve audio reproduction. It also delivers 1.1W to the speaker differentially through a bridge-tied-load output stage. This provides up to four times more output power than a conventional, single-ended output stage, thus eliminating the need for output-coupling capacitors and further minimizing external component count. The amplifier achieves a 90dB PSRR at 1kHz. Moreover, it features a flexible, single-wire, serial pulse interface to realize gain settings from -9dB to 18dB in 3dB steps and it integrates click-and-pop suppression for rich, clean sound quality.

MAX8678 is fully specified for the extended temperature range of -40C to 85C. Prices start at $1.65 for 2,500-unit quantities. An evaluation kit is available to speed designs.

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