User's Manual

page 14/51
HiAll
NC
User Manual 2012/06/28
3.3 AUDIOS
The HiAll
NC
module provides both analogue and digital audio interfaces.
3.3.1 Analogue audio connection
HiAll
NC
module features one input path and one output path for analogue audio. Both the input path and the
output path are differential. The design examples in the following chapter will take into account the EMC, ESD
protections, and reducing the possible TDMA noise in sensitive area by performing the given routing rules.
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Note that acoustic engineering competences are mandatory to get accurate audio performance on
customer’s product.
3.3.1.1 Connecting microphone and speaker
HiAll
NC
module can manage an external microphone (MIC_P/MIC_N) in differential 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 1.4V voltage to bias the microphone is implemented in the module.
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The speaker connected to the module should be 32 ohms.
ESD protection
Figure 5: Analogue audio connection
If the design is ESD or EMC sensitive, we strongly recommend reading the notes below.
A poor audio quality could either come from the PCB routing and placement or from the chosen components (or
even both).
3.3.1.1.1 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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As described in the layout chapter, differential pairs must be routed in parallel and same length (MIC_P
and MIC_N signals)
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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. 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)
HiAllNC
Speaker
MIC