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Headphone amps pack built-in protection circuitry

Posted: 05 May 2009 ?? ?Print Version ?Bookmark and Share

Keywords:headphone amplifier? automotive? circuitry protection?

Maxim Integrated Products has introduced the MAX13330/MAX13331 stereo headphone amplifiers that protect outputs against shorts to battery/ground and load dump up to 45V. The devices are designed for automotive entertainment systems, in which board space is at a premium and high-voltage protection is paramount.

The built-in protection circuitry eliminates the need for the discrete components that perform such protection, resulting in both space and cost savings. They also integrate short-circuit diagnostic output to facilitate fault analysis, and include 15kV ESD protection (Human Body Model) on the headphone outputs. These advanced protection and diagnostic features make the MAX13330/MAX13331 the ideal choice for automotive entertainment systems.

The MAX13330/MAX13331 employ Maxim's patented DirectDrive technology to dramatically reduce BOM cost and save board space. DirectDrive headphone amplifiers produce a ground-referenced output from a single supply, and therefore do not require a DC bias voltage to be applied to the headphone-jack ground pin. This innovative approach eliminates the need for the large DC-blocking capacitors required by conventional amplifiers, thus enabling the MAX13330/MAX13331 to save up to $0.10 in cost, 150mm? of board space, and 8mm of component height. Moreover, not using DC-blocking capacitors allows improvement of the amplifiers' low-frequency response for successful reproduction of the full range of audio bandwidth with only a 1microfarad or smaller capacitor. This capability is especially important for music playback. Ultimately, the MAX13330/MAX13331 significantly simplify end-product design while maximizing reliability.

The gain of the amplifiers can also be set internally (-1.5V/V, MAX13330) or adjusted externally (MAX13331), providing flexibility in audio codec selection. Both devices operate from a single, 4V to 5.5V supply; have a low, 0.009 percent THD+N; and can deliver up to 75mW per channel into an 8? load, 100mW into a 16? load, or 130mW into a 32? load. An 80dB at 217Hz PSRR allows these devices to operate from noisy digital supplies without an additional linear regulator or filtering. Comprehensive click-and-pop circuitry suppresses audible clicks and pops on startup and shutdown, ensuring fast turn-on/turn-off times without audible glitches. A low-power shutdown mode reduces the supply current to Fully specified over the -40C to +105C AEC-Q100 Level 2 automotive temperature range, the MAX13330/MAX13331 are available in a space-saving, 4mm x 5mm, 16-pin QSOP package. Prices start at $1 (1,000-up, FOB USA).

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