AD1847

The AD1847 SoundPort^® Stereo Codec integrates key audio ata conversion and control functions into a single integrated ircuit. The AD1847 is intended to provide a complete, low ost, single-chip solution for business, game audio and multimedia pplications requiring operation from a single +5 V supply.It provides a serial interface for implementation on a omputer motherboard, add-in or PCMCIA card. See Figure 1 or an example system diagram.

External circuit requirements are limited to a minimal number f low cost support components. Anti-imaging DAC output ilters are incorporated on-chip. Dynamic range exceeds 70 dB ver the 20 kHz audio band. Sample rates from 5.5 kHz to 8 kHz are supported from external crystals.

The Codec includes a stereo pair of analog-to-digital converters ADCs) and a stereo pair of digital-to-analog converters DACs). Inputs to the ADC can be selected from four tereo pairs of analog signals: line 1, line 2, auxiliary ("aux") ine #1, and post-mixed DAC output. A software-controlled rogrammable gain stage allows independent gain for each hannel going into the ADC. The ADCs' output can be digitally ixed with the DACs' input.

The pair of 16-bit outputs from the ADCs is available over a serial nterface that also supports 16-bit digital input to the DACs nd control/status information. The AD1847 can accept and enerate 16-bit twos-complement PCM linear digital data, 8-bit nsigned magnitude PCM linear data, and 8-bit m-law or A-law ompanded digital data.

The DACs are preceded by a digital interpolation filter. An ttenuator provides independent user volume control over each AC channel. Nyquist images are removed from the DACs' nalog stereo output by on-chip switched-capacitor and ontinuous-time filters. Two stereo pairs of auxiliary line-level nputs can also be mixed in the analog domain with the DAC utput.

The AD1847 serial data interface uses a Time Division Multiplex TDM) scheme that is compatible with DSP serial ports onfigured in Multi-Channel Mode with 32 16-bit time slots i.e., SPORT0 on the ADSP-2101, ADSP-2115, etc.).