Cirrus Logic CRD4297-1 AMR, Product Data Book

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2 DS242RD1B1
CRD4297-1 AMR
CrystalClear™ AC '97 AMR Audio Modem Riser Reference
CIRRUS LOGIC ADVANCED PRODUCT DATABOOK
GENERAL INFORMATION
The CRD4297-1 AMR is a production-grade
AMR audio card reference design using the
CS4297 SoundFusion Audio Codec ‘97. The de-
sign supports the functionally compatible CS4297,
CS4297A, or CS4299 AC ‘97 SoundFusion Audio
Codecs.
The AMR board advantage lies in the complete
separation of the analog section from the noisy dig-
ital environment of a personal computer. A 5-wire
digital link is all that is required to connect the au-
dio codec to the AMR bus-based AC ‘97 controller.
This allows the audio section to reach the required
dynamic range of ~90 dB FS A while making the
layout and placement of the audio section easier to
implement. The CS4297 performs the Digital-to-
Analog Conversion (DAC) for the digital audio
output stream and also provides multiple analog
audio inputs and outputs, analog mixing and Ana-
log-to- Digital Conversion (ADC).
This card is designed to provide the highest possi-
ble functionality, along with industry leading audio
performance at a low manufacturing cost. Care was
taken with component placement and signal rout-
ing to minimize sources that can degrade audio per-
formance. Cirrus’ analog design know-how has
resulted in a board that preserves the exceptional
analog performance of the CS4297.
REFERENCE DESIGN FEATURES
The CRD4297-1 AMR reference design illustrates
a high quality, low cost two-layer add-in card lay-
out. The card is sectioned into three main parts: the
AMR bus section, the CS4297 Audio Codec ‘97
section, and the Analog I/O section.
Digital Audio Out
The AMR bus provides digital out in a format com-
patible with the consumer portion of IEC 958. An
older version of this standard is also known as
S/PDIF. Depending upon the codec, the SPDIF sig-
nal originates either from the AMR bus or the co-
dec. Digital out is provided through a Toshiba
TOTX173 optical TOS-LINK jack on the board
edge. There are many advantages in using a Fiber
optic link versus the traditional coaxial link. Fiber
optic is a non-metallic insulator thereby preventing
ground loops and electromagnetic interference.
For signal transmission, it offers low attenuation,
high bandwidth, low propagation delay, low bit er-
ror rates, small size, and cost efficiency. The signal
is IEC 958 and CP-1201 compliant.
CS4297 Audio Codec
‘97
The CS4297 is a mixed-signal serial Codec based
on the AC ‘97 specification. It is designed to be
paired with a digital controller, located on the
AMR bus. The AC ‘97 Controller is responsible for
all communications between the CS4297 and the
rest of the system. The CS4297 functions as an an-
SoundFusion and CrystalClear are trademarks of Cirrus Logic, Inc.
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Preliminary product information describes products which are in production, but for which full characterization data is not yet available.
Advance product information describes products which are in development and subject to development changes. Cirrus Logic, Inc.
has made best efforts to ensure that the information contained in this document is accurate and reliable. However, the information is
subject to change without notice and is provided “AS IS” without warranty of any kind (express or implied). No responsibility is as-
sumed by Cirrus Logic, Inc. for the use of this information, nor for infringements of patents or other rights of third parties. This docu-
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