User's Manual

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Note d’étude / Technical document : URD1– OTL 5665.1– 002 / 70 884 Edition 03
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8. RECOMMENDATIONS ON LAYOUT OF CUSTOMER’S BOARD
8.1 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
(1).
... Therefore it is very important to respect some rules to
avoid disruptions or abnormal behaviour.
8.1.1 Ground

A ground plane as complete as possible

Ground of components has to be connected to the ground layer through many vias not regularly distributed.

Top and bottom layer shall have as much as possible of ground planes.
8.1.2 Power supplies

Plan for power supply signals (VBAT, VGPIO), no loop.

Suitable power supply (VBAT, VGPIO) track width, thickness.
8.1.3 Clocks
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Clock signals must be shielded between two grounds plans and bordered with ground vias.
8.1.4 Data bus and other signals
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Data bus and commands have to be routed on the same plane, none of the lines of the bus shall be
parallel to other lines
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Lines crossing shall be perpendicular
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Suitable other signals track width, thickness.

Data bus must be protected by upper and lower ground plans
8.1.5 Radio

Provide a 50 Ohm microstrip line for antenna connection
8.1.6 Audio (see also § 10.2)
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Differential signals have to be routed together, parallel (for example HSET_OUT_P/HSET_OUT_N).
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Audio signals have to be isolated, by pair, from all the other signals (ground all around each pair).
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Cancel any loops between VBAT and GND next to the speaker to avoid the TDMA burst noise in the
speaker during a communication.
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The single-end audio signal should be adopted the same rules as differential signals.