User's Manual

page 14/64

Note d’étude / Technical document : URD1– OTL

5665.3

– 003 / 72238 Edition 01

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4.2.1.1 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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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)

Figure 8 : Filter and ESD protection of microphone

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To use an external bias voltage for the microphone, simply use a capacitor of 10µF to prevent this bias

voltage to be re-injected inside the module.

4.2.1.2 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.

Figure 9: Filter and ESD protection of 32 ohms speaker

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HSET_OUT_P, HSET_OUT_N tracks must be larger than other tracks: 0.1 mm.

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As described in the layout chapter, differential signals have to be routed in parallel (HSET_OUT_P and

HSET_OUT_N signals)

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The impedance of audio chain (filter + speaker) must be lower than 32Ω.

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To use an external audio amplifier connected to a loud-speaker, use serial capacitors of 10nF on HiLoNC

audio outputs to connect the audio amplifier.

HiLoNC V2

INTMIC_P

MIC

Ferrite Bead

18pF

ESD protection

HiLoNC V2

HSET_OUT_P

HSET_OUT_N

speaker

Ferrite Bead

18pF

ESD protection