Layout Consideration; Figure 28 Hda Example Schematic - Emerson COM Express Carrier Design Manual

Figure 27 HDA Example Schematic

13.3 Layout Consideration

The following is a list of basic recommendations:
 Traces must be routed with a target impedance of 55 ohms, and an allowed tolerance of ±15%.
 Ground return paths for the analog signals must be given special consideration.
 Digital signals routed in the vicinity of the analog audio signals must not cross the power plane split
lines. Locate the analog and digital signals as far as possible from each other.
 Partition the carrier board with all analog components grouped together in one area and all digital
components in another.
 Keep digital signal traces, especially the clock, as far as possible from the analog input and voltage
reference pins.
 Provide separate analog and digital ground planes 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 in wide.
 Route analog power and signal traces over the analog ground plane.
 Route digital power and signal traces over the digital ground plane.
 Position the bypassing and decoupling capacitors close to the IC pins with wide traces to reduce
impedance.
 Place the crystal or oscillator (depending on the codec used) as close as possible to the codec.(HDA
implementations generally do not require a crystal at the codec)
Page 72 of 103 COM Express Carrier Type 2
Design Guide