GD82559C Datasheet, PDF (18/60 Pages) Intel Corporation – Intel-Based Electronic Classroom Student Computing Station Based on the Intel® Celeron™ Processor and Intel® 810 Chipset

Intel-Based Electronic Classroom Student Computing Station
5.4.1
5.5
5.5.1
Design Notes for AC’97 Devices
• Special consideration must be given for the ground return paths for the analog signals. If
isolated ground planes are used, pin B2 on the AMR connector should be used as an isolated
ground pin and should be connected to an isolated ground plane to reduce noise in the analog
circuits. The AMR designer and motherboard designer should jointly address any EMI issues
when implementing isolated grounds.
• Digital signals routed in the vicinity of the analog audio signals must not cross the power plane
split lines. Analog and digital signals should be located as far as possible from each other.
• Partition the board with all analog components grouped together in one area and all digital
components in the other.
• Separate analog and digital ground planes should be provided, with the digital components
over the digital ground plane, and the analog components, including the analog power
regulators, over the analog ground plane. The split between the planes must be a minimum of
0.05” wide.
• Keep digital signal traces, especially the clock, as far way from analog input and voltage
reference pins as possible.
• Do not completely isolate the analog/audio ground plane from the rest of the board ground
plane. There should be a single point (¼” to ½ ” wide) where the analog/isolated ground plane
connects to the main ground plane. The split between the planes must be a minimum of
0.05”wide.
• Any signals entering or leaving the analog area must cross the ground split in the area where
the analog ground is attached to the main motherboard ground (i.e., there should not be any
signals crossing the split/gap between the ground planes). Doing so will cause a ground loop.
Audio/Modem Riser Card (AMR)
Intel is developing a common connector specification known as the Audio/Modem Riser (AMR).
This specification defines a mechanism for allowing OEM plug-in card options. The AMR
specification is available on the Intel developer website:
http://developer.intel.com/pc-supp/platform/ac97/index.htm
The AMR specification provides a mechanism for AC’97 codecs to be on a riser card. This is
important for modem codecs as it helps ease international certification of the modem.
For the Intel-based electronic classroom student computing station, the audio codec is integrated on
the motherboard to avoid compatibility issues and robustness. A modem codec is optional for
electronics classroom.
Design Notes for the Audio/Modem Riser Card
• Only one primary codec can be present on the link. A maximum of two present codecs can be
supported in an ICH platform.
• As the Intel-based electronic classroom student computing station motherboard implements an
active primary codec (audio) on the motherboard and provides an AMR connector, it must tie
PRI_DN# to ground. The PRI_DN# pin is provided to indicate that a primary codec is present
on the motherboard.
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Application Note