Audio codec has a split personality

A new stereo audio codec offers the ability to operate the ADC and DAC at different sample rates simultaneously, making it ideal for simultaneous playback and recording applications.

Wolfson Microelectronics has launched a new stereo audio codec with the ability to operate the ADC and DAC at different sample rates simultaneously, making it ideal for use in DVD-RW, LCD TV, and similar consumer electronics applications, where the end user requires to simultaneously play and record DVD or television content.

This feature of the Wolfson WM8591 codec allows a single small codec chip to be used in place of two separate ADC and DAC devices, offering designers the potential to save component cost, external component count and PCB area over existing solutions.

The WM8591 also includes an analogue programmable gain amplifier (PGA).

The PGA can be used to adjust the sensitivity of analogue inputs ensuring that recording levels are consistent, and also used as a limiter to avoid analogue input overload distortion.

The WM8591 is a single-ended input, two-wire control version of the WM8590 with an impressive DAC signal-noise ratio (SNR) of 110dB combined with a 102dB ADC.

Unlike many conventional solutions, which require multiple control systems, this single two-wire interface offers access to all features including volume control and mute and de-emphasis facilities, significantly reducing design time.

The single-ended inputs to the ADC and differential outputs from the DAC further support designers in achieving high performance with reduced system complexity.

Like the WM8590, the new WM8591 is based on a 24bit sigma-delta ADC with programmable input gain and limiter control.

analogue gain can be adjusted from +24 to -21dB in 0.5dB steps, and digital gain can be programmed from -21.5dB to -103dB, also in 0.5dB steps.

Output word lengths from 16 to 32bit are supported, along with sampling rates from 32 to 96kHz.

The device's audio data interface supports IsqdS, left-justified, right-justified and DSP formats.

The DAC supports sampling rates from 32 to 192kHz, which can be programmed independently of the ADC sample rate.

The Wolfson WM8591 is available to sample now and will be available in volume in Q4 2005.

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