RK3288 Hardware Design Guide
17.2 PCB Layout
Line width of all Codec power supply is requested to be above 15mils，VCC_SPK trace
width should be above 30mils.
Each analog signals input/output from Codec, including HP out, LINE in, LINE out, MIC
in, SPDIF and Speaker out signals, need to be surrounded by GND ( including peer
layers and adjacent layer) to avoid output distortion and noise, also need to be
separated from other digital signals.
HP output signal line width suggested to be above 15mils.
LINE in/out signal trace width suggested to be above 10mils.
MIC input signal is sensitive, MIC coupling capacitor should be placed close to Codec
to avoid noise as shown in Fig 17-5.
Fig 17-5
Codec should be placed close to connecting base.
To suppress EMI, trace length from power amplifier to speaker should be the shorter,
the better, trace width should be wider with less angle. To avoid noise jamming,
suggest to route differential traces with above 20mils trace width, less than 10mils,
and a LC filter circuit should be reserved closed to speaker input terminal.
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