User's Manual

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Note d’étude / Technical document : URDx– OTL 5635.1– 007 / 70 230 Edition 03
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connected to the module. The bias supply to microphone is implemented in the module. The speaker connected
to the module should be 32 ohms.
Figure 4: Audio connection
If the design is ESD or EMC sensitive we strongly recommend to read the notes below.
The weakness can either come from the PCB routing and placement or from the chosen components (or both).
3.2.1.1 Notes for microphone:
• Pay attention to the microphone device, It must not be sensitive to RF disturbances.
• Some microphone includes two spatial microphones inside the same shell and allow to make an
electrical difference between the environment noise (received by one of the two mic.) and the active
signal (received by the other mic. + noise) resulting in a very high SNR.
• If you need to have deported microphone out of the board with long wires, you should pay attention to
the EMC and ESD effect. It also the case when your design is ESD sensitive. In those cases, add the
following protections to improve your design.
• To ensure proper operation of such sensitive signals, they have to be isolated from the others by
analogue ground on mother board layout. (Refer to Layout design chapter)
Figure 5 : Filter and ESD protection of microphone
3.2.1.2 Notes for speaker:
• As explained for the microphone, if the speaker is deported out of the board or is sensitive to ESD, use
the schematic here after to improve the audio.
• HSET_OUT_P, HSET_OUT_N, and tracks must be larger than other tracks: 0.1 mm.
• As described in the layout chapter, differential signals have to be routed in parallel: it is the case for
HSET_OUT_P and HSET_OUT_N.
HiLo
Filter and
ESD
protection
HSET_OUT_P
HSET_OUT_N
INTMIC_P
32ohms speaker
MIC
HiLo
INTMIC_P
MIC
Ferrite Bead
18pF
ESD protection