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Maxim’s stereo audio D/A design cuts component count

Sunnyvale, Calif. — Aimed at portable applications, Maxim Integrated Products Inc.'s MAX9850, a 1.8-V stereo audio digital-to-analog (D/A converter), features a patented design that eliminates bulky capacitors and crystal oscillators.

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

Maxim's patented DirectDrive architecture produces a ground-referenced output from a single supply, thus eliminating the two bulky DC-blocking capacitors commonly used between the amplifier and the headphone. The removal of the two large caps makes more efficient use of board space-up to eight times less than alternative solutions.

Additionally, driving the audio signal directly to the headphone enhances the low-frequency response of the system, leading to full-range audio reproduction, especially important for music and video playback. The DirectDrive architecture does not require the headphone jack to be biased to a DC voltage and it allows a conventional, grounded chassis design, thereby greatly simplifying system design and improving long-term reliability.

Another unique MAX9850 feature is innovative output-clocking circuitry that derives all common audio rates from an arbitrary master clock up to 40 MHz. The flexible architecture uses any available system clock and eliminates the need for an external phase- locked loop (PLL) and multiple crystal oscillators. The device supports a wide range of sample rates from 8 kHz to 48 kHz in both master and slave modes, making the MAX9850 the easiest to use and most versatile audio D/A converter available.

The device supports common I²C-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 high power supply rejection ratio (PSRR) rate of 100 dB allows the part to operate directly from noisy supplies, eliminating the need for a dedicated low dropout (LDO). To simplify the design and reduce system cost further, the MAX9850 features -73 dB to +6 dB volume control that uses I² C to adjust the gain of the output amplifier and eliminate the need for an external potentiometer.

The MAX9850 is available in the thermally efficient, 5 x 5 mm, 28-pin TQFN packages for general portable-audio applications. This device operates over the industrial temperature range (-40°C to +85°C).

Pricing begins at $1.75 (1000-up, FOB USA).

Purchase of I²C components from Maxim Integrated Products, Inc., or one of its sublicensed Associated Companies, conveys a license under
the Philips I²C Patent Rights to use these components in an I²C system, provided that the system conforms to the I²C Standard Specification as defined by Philips.

Click here for a data sheet of the MAX9850.

For more information, readers can call 1-800-998-8800 or visit: www.maxim-ic.com.

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