AD1881JST Datasheet, PDF (10/22 Pages) Analog Devices – AC 97 SoundMAX Codec

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AD1881
PRODUCT OVERVIEW
Analog-to-Digital Signal Path
The ADI881 is the flISt audio Codec to meet the Audio Codec
The selector sends left and right channel information to the
'972.0 and 2.1 Extensions. In addition, the AD 1881 SoundMAX
Codec is designed to meet all requirements of the Audio Codec
programmable gain amplifier (PGA). The PGA following the
selector allows independent gain control for each channel enter-
'97, Componenr Specijia2rion, Revision 1.03, I{;)1996, Intel Cor-
poration, found at www.lmd.com. The ADI881 also includes
some other Codec enhanced features such as communicating
ing the ADC from 0 dB to +22.5 dB in 1.5 dB steps. Each
channel of the ADC is independent, and can process left and
right channel data at different sample rates.
to three Codecs on the same link, a DSP serial port mode,
modem sample rates and filtering, and built-in Phat Stereo 3D
enhancement.
S3II1ple Rates and D2S
The AD 1881 default mode sets the Codec to operate at 48 kHz
sample rates. The converter pairs may process left and right
The AD 1881 is an analog front end for high performance PC
channel data at different sample rates. The ADI881 sample rate
audio, modem, or DSP applications. The AC '97 architecture
generator allows the Codec to instantaneously change and pro-
derIDes a 2-chip audio solution comprising a digital audio
cess sample rates from 7 kHz to 48 kHz with a resolution of
OBSOLETE ^{controller, plus a high quality analog component that includes}
Digital-to-Analog Converters (DACs), Analog-tO-Digital Con-
verters (ADCs), mixer and I/O.
The main architectural features of the AD 1881 are the high
quality analog mixer section, two channels of~ ADC conver-
sion, two channels of~ DAC conversion and Data Direct
Scrambling (D2S) rate generators. The AD1881's left channel
ADC and DAC are compatible for modem applications supporting
irrational sample rates and modem filtering requirements.
FUNCTIONAL DESCRIPTION
This section overviews the functionality of the AD 1881 and is
intended as a general introduction to the capabilities of the
device. Detailed reference information may be found in the
descriptions of the Indexed Control Registers.
Analog Inputs
The Codec contains a stereo pair of~ ADCs. Inputs to the
ADC may be selected from the following analog signals: tele-
I Hz. The in-band integrated noise and distortion arrifacts
introduced by rate conversions are below --90 dB. The ADl881
uses a 4-bit D/A structure and Data Directed Scrambling (D2S)
to enhance noise immunity on motherboards and in PC enclo-
sures, and to suppress idle tones below the device's quantization
noise floor. The nzs process pushes noise and distortion arti-
facts caused by errors in the multibit DAC to frequencies be-
yond the auditory response of the human ear and then filters
them.
Digital-to-Analog Signal Path
The analog output of the DAC may be gained or attenuated
from +12 dB to -34.5 dB in 1.5 dB steps, and summed with any
of the analog input signals. The summed analog signal enters
the Master Volume stage where each channel of the mixer out-
put maybe attenuated from 0 dB to -94.5 dB in 1.5 dB steps or
muted.
line-Level Outputs
The ADl88l offers a ttue line-level output for notebook dock-
phony (PHONE_IN), mono microphone (MICI or MIC2),
ing station and home theater applications. The line-level output
stereo line (UNE_IN), auxiliary line input (AUX), stereo CD
does not change with master volume settings.
ROM (CD), stereo audio from a video source (VIDEO) and
post-mixed stereo or mono line output CUNE_OUT).
Host-Based Echo Cancellation Support
The AD188l supports time correlated I/O data format by pre-
Analog Mixing
senting MIC data on the left channel of the ADC and the mono
PHONE_IN, MICI or MIC2, UNE_IN, AUX, CD and
summation of left and right output on the right channel. The
VIDEO can be mixed in the analog domain with the stereo
output from the DACs. Each channel of the stereo analog in-
ADC is splittable; left and right ADC data can be sampled at
different rates.
puts may be independently gained or attenuated from + 12 dB to
-34.5 dB in 1.5 dB steps. The summing path for the mono
inputs (PHONE_IN, MICI, and MIC2 to UNE_OUT) dupli-
cates mono channel data on both the left and right UNE_OUT.
Additionally, the PC attention signal (PC_BEEP) may be mixed
Power Management Modes
The ADl88l is designed to meet ACPI power consumption
requirements through flexible power management control of an
internal resources.
with the line output. A switch allows the output of the DACs to
bypass the Phat Stereo 3D enhancement.
Digital Audio Mode
The ADI881 is designed with a Digital Audio Mode (DAM)
that allows mixing of all analog inputs independent of the DAC
output signal path. Mixed analog input signals may be sent to
the ADCs for processing by the controller or the host, and may
be used during simultaneous capture and playback at different
sample rates.
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