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Maxim audio DAC with built-in DirectDrive headphone amplifiers

Posted: 01 Dec 2004 ?? ?Print Version ?Bookmark and Share

Keywords:maxim integrated products? max9850? stereo audio dac?

Maxim Integrated Products expanded its line of audio integrated circuits with the release of the MAX9850 stereo audio DAC.

The MAX9850 features built-in DirectDrive headphone amplifiers and operates from any 1.8V to 3.6V single supply. Optimized for low-voltage operation, it delivers 30mW of output power from a 1.8V supply. It is designed to meet the board-space and performance requirements of portable devices such as cellphones, MP3 players and portable DVD players.

The new audio DAC uses the company's patented DirectDrive architecture that produces a ground-referenced output from a single supply, eliminating the two bulky DC-blocking capacitors commonly used between the amplifier and the headphone, Maxim said. The removal of the two large caps makes more efficient use of board space-up to eight times less than alternative solutions, it added. In addition, driving the audio signal directly to the headphone enhances the low-frequency response of the system, leading to full-range audio reproduction. The DirectDrive architecture also does not require the headphone jack to be biased to a DC voltage and it allows a conventional, grounded chassis design, thereby simplifying system design and improving long-term reliability.

The MAX9850 also features an output-clocking circuitry that derives all common audio rates from an arbitrary master clock up to 40MHz. The architecture uses any available system clock, and eliminates the need for an external PLL and multiple crystal oscillators. The device also supports a wide range of sample rates from 8kHz to 48kHz in both master and slave modes, making the MAX9850 one of the easiest to use and most versatile audio DAC available.

The new device supports common I?C-compatible audio interfaces. Stereo-audio line inputs are provided either to mix analog audio with the digital input stream, or to drive the headphone or line outputs directly. A PSRR rate of 100dB allows the product to operate directly from noisy supplies, eliminating the need for a dedicated LDO. Additionally, the MAX9850 features a -73dB to 6dB volume control that uses I?C to adjust the gain of the output amplifier and eliminate the need for an external potentiometer.

The MAX9850 operates over the industrial temperature range. It is available in the thermally efficient, 5-by-5mm, 28-pin TQFN packages suitable for general portable-audio applications, with pricing starting at $1.75 (1,000-up, FOB USA).

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