Analog Devices, Inc. introduced the AD1855, a single-chip, stereo digital audio playback system, capable of sampling data at 16, 18, 20 or 24 bits. This monolithic digital-to-analog converter (DAC) system comprises a multibit sigma-delta modulator with dither, continuous time analog filters, analog output drive circuitry and click-less volume control and mute. The AD1855 achieves 113-dB dynamic range and signal-to-noise ratio (not muted) at 48 kHz (110 dB at 96 kHz), and -97-dB total harmonic distortion + noise, providing perfect differential linearity restoration for reduced idle tones and noise floor in a variety of consumer and professional applications. The high performance and low price makes the AD1855 well-suited for digital versatile disk (DVD) players, A/V receivers, digital car audio systems, surround sound home theater systems, high-end CD players, as well as "prosumer" and professional equipment such as digital mixing consoles.

The AD1855 gluelessly connects to Analog Devices' popular SHARC family of 32-bit DSPs, using either the serial port or via the I²S ports on the ADSP-21065L ($10 SHARC). The AD1855 can also be used with any DSP processor, audio processor or decoder that outputs data in the I²S 3-wire format. Left-justified, right-justified (16-bit) and DSP serial port modes are also supported. In addition, the AD1855 is fully compatible with all current DVD formats, including 96-kHz sample frequency and 24 bits. Backwards compatibility is achieved by supporting 50 ýs/15 ýs digital de-emphasis intended for "redbook" 44.1-kHz sample frequency playback from compact discs.

The AD1855 has a simple but very flexible serial data input port that allows for glueless interconnection to a variety of analog-to-digital converters (ADCs), digital signal processors (DSPs), AES/EBU receivers and sample rate converters. The AD1855 accepts serial audio data in most significant bit first, two's-complement format. This multibit DAC operates from a single +5-V power supply, with a power-down mode to minimize power consumption when the device is inactive.

Dual data directed scrambling and a 64-level multibit modulator reduces sensitivity to jitters and out-of-band noise and simplifies output filtering. Sigma-delta conversion with a continuous time output stage offers higher SNR in a smaller die.

I cannot see anything that ADI has done wrong with this part; they are later than one other company into this DVD arena and that may have cost them some of the second-generation market: We will have to see. The magic number of 113 dB for dynamic range and SNR has also been exceeded elsewhere but the differences are getting to a point where the actual layout will not allow these sorts of numbers to be measured anyway, whatever the manufacturer's suggested layouts look like. I would expect to see the next improvement in numbers will be in getting THD+Noise over the 100 dB-level.

This part does it right with good professional-audio numbers and specs at a good consumer-level product price: And ADI are finally learning that they better push the DSP solution with the analog/mixed-signal parts. They will sell $15-20 of analog parts with every $10 of DSP when they really do get it done totally seamlessly.

The AD1855 is available in a 28-lead SSOP and is priced at $3.95 in 10,000-piece lots.