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Qseven RISC Carrier Board Design Guide
the voltage coefficient, temperature coefficient, and noise are not factors.
●
Locate the crystal or oscillation closed to the codec.
● The I2S Audio trace impedance from codec to ROM-7420 Module should be 50 Ω
± 10%.
3.2.3.2 EMI Considerations
The signals entering or leaving the analog area must cross the ground split through
the beads between digital ground and analog ground. No signal can cross the
split/gap between the ground planes, which will cause a ground loop and greatly
increase EMI emissions and degrade the analog and digital signal quality.
3.2.3.3 Grounding Techniques
Take care the grounding of the audio jacks, especially the line-in and microphone
jacks. Avoid grounding the audio jacks to the ground plane directly under the
connectors. Otherwise, the potential of audio noise voltage will be induced into the
inputs due to the ground potential difference between the audio jacks ground and the
codec’s ground. Figure 3-11 shows the grounding example for layout..
Figure 3-11 Audio Ground Guidelines