AD1848K

The Parallel-Port AD1848K SoundPort^® Stereo Codec integrates he key audio data conversion and control functions into  single integrated circuit. The AD1848K is intended to provide  complete, single-chip audio solution for business audio and ultimedia applications requiring operation from a single +5 V supply. It provides a direct, byte-wide interface to both ISA "AT") and EISA computer buses for simplified implementation n a computer motherboard or add-in card. The AD1848K enerates enable and direction controls for IC buffers such as 4_245.

The AD1848K SoundPort Stereo Codec supports a DMA request/grant architecture for transferring data with the host computer us. One or two DMA channels can be supported. rogrammed I/O (PIO) mode is also supported for control egister accesses and for applications lacking DMA control. Two nput control lines support mixed direct and indirect addressing f twenty-one internal control registers over this asynchronous nterface.

xternal circuit requirements are limited to a minimal number f low cost support components. Anti-imaging DAC output filters re incorporated on-chip. Dynamic range exceeds 80 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 onverters and a stereo pair of digital-to-analog converters. nputs to the ADC can be selected from four stereo pairs of analog signals: line, microphone ("mic"), auxiliary ("aux") #1, nd post-mixed DAC output. The microphone inputs can pass hrough optional 20 dB gain blocks. A software-controlled programmable ain stage allows independent gain for each channel oing into the ADC. The ADCs' output can be digitally mixed ith the DACs' input.

The pair of 16-bit outputs from the ADCs is available over a yte-wide bidirectional interface that also supports 16-bit digital nput to the DACs and control information. The AD1848K can ccept and generate 16-bit twos-complement PCM linear digital ata, 8-bit unsigned magnitude PCM linear data, and 8-bit -law or A-law companded digital data.

The DACs are preceded by a digital interpolation filter. An ttenuator provides independent user volume control over each AC channel. Nyquist images and shaped quantization noise re removed from the DACs' analog stereo output by on-chip witched-capacitor and continuous-time filters. Two stereo pairs f auxiliary line-level inputs can also be mixed in the analog domain ith the DAC output.