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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3.2 HOW TO CONNECT THE AUDIOS?
The HiloNC module features one input audio path and one output audio path. The input path is single-end while
the output path is differential. In this following chapter examples of design will be given including protections
against EMC and ESD and some notes about the routing rules to follow to avoid the TDMA noise usually present
in this sensitive area of design.
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Please note that acoustic competences are mandatory to get accurate audio performance on customer’s
product.
3.2.1 Connecting microphone and speaker
The HiloNC module can manage an external microphone (INTMIC_P) in single-end mode and an external
speaker (HSET_OUT_P / HSET_OUT_N) in differential mode. Thus, one speaker and one microphone can be
connected to the module. The bias supply to microphone is implemented in the module.
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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
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Pay attention to the microphone device, it must not be sensitive to RF disturbances.
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Some microphones include 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.
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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 is also the case when your design is ESD sensitive. In those cases, add the
following protections to improve your design.
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To ensure proper operation of such sensitive signals, they have to be isolated from the others by analogue
ground on customer’s board layout. (Refer to Layout design chapter)
HiloNC
Filter and
ESD
protection
HSET_OUT_P
HSET_OUT_N
INTMIC_P
32ohms speaker
MIC