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Audio amplifiers detect headphone input

Posted: 16 May 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Maxim? amplifier? audio? stereo? MAX9777?

Maxim Integrated Products has introduced two highly-integrated audio amplifiersthe MAX9777 and MAX9778that combine a stereo 3W bridge-tied load audio amplifier, stereo headphone amp, headphone sensing and a 2:1 input multiplexer.

The MAX9777 has an I2 interface and the MAX9778 has a parallel-control interface. Both devices are available in a 28-pin 5-by-5-by-0.8mm TQFN package. These audio amplifiers are designed for portable and low-power-output applications such as notebook computers, multimedia monitors and DVD players.

The MAX9777/MAX9778 operate from a 4.5V to 5.5V single supply and feature a 100dB PSRR, which allows operation from noisy supplies without adding a linear regulator. Maxim said the 0.002 percent THD+N of the devices ensures clean, low-distortion amplification of the audio signal. Patented click-and-pop suppression eliminates audible transients on power and shutdown cycles.

Power-saving features include a 10mV offset voltage to minimize DC current drain through the speakers, a 13mA supply current, and a 10?A shutdown mode. A mute function allows the outputs to be quickly enabled or disabled.

For design flexibility, a headphone-sense input automatically detects the presence of a headphone jack and configures the amplifiers for either speaker or headphone mode. To compensate for limitations in the frequency response of the loudspeakers, the integrated 2:1 input multiplexer makes it easy to select from multiple audio sources or an external equalizer network. The various functions are controlled by either the I2C-compatible or simple parallel-control interface.

The MAX9777 and MAX9778 are available in a thermally-efficient, 28-pin QFN package. Both devices have complete thermal overload protection, and are specified over a temperature range of -40C to 85C. Prices start at $1.25 (1,000-up, FOB USA).

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