User's Manual

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Note d’étude / Technical document : URD1– OTL
5665.3 – 003 / 72238 Edition 01
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As audio input and output are strongly linked:
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Place the microphone and the speaker as far as possible from one another.
8.2 ELECTRONICS AND LAYOUT
Avoid Distortion & Burst noise
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Audio signals must be symmetric (same components on each path).
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Differential signals must be routed parallel.
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Audio layer must be surrounded by 2 ground layers.
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The link from one component to the ground must be as short as possible.
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If possible separate the PCB of the microphone and the one of the speaker.
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Reduce as much as possible the number of electronics components (loss of quality, more dispersion).
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Audio tracks must be larger than 0.5 mm.
9. RECOMMENDATIONS ON LAYOUT OF CUSTOMER’S BOARD
9.1 GENERAL RECOMMENDATIONS ON LAYOUT
There are many different types of signals in the module which are disturbing each other. Particularly, Audio
signals are very sensitive to external signals as VBAT... Therefore it is very important to respect some rules to
avoid disruptions or abnormal behaviour.
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Magnetic field generated by VBAT tracks may disturb the speaker, causing audio burst noise. In this case,
modify layout of the VBAT tracks to reduce the phenomena.
9.1.1 Ground
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A ground plane as complete as possible
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Ground of components has to be connected to the ground layer through many vias not regularly
distributed.
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Top and bottom layer shall have as much as possible of ground planes. Flood the empty remain surface
of the layout of those two layers with a ground plane connected to main ground with as much vias as possible.
9.1.2 Power supplies
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Layer for power supply signals (VBAT, VGPIO) is recommended.
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Any loop of power signals layout must be avoided on the design.
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Suitable power supply (VBAT, VGPIO) track width and thickness.