Reference Circuit Design For Headphone Interface; Reference Circuit Design For Loudspeaker Interface; Audio Interfaces Design Considerations - Quectel SC66 Hardware Design

3.22.3. Reference Circuit Design for Headphone Interface

MIC_GND
F1
MIC2_P
HPH_L
R2
HS_DET
20K
HPH_R
HPH_REF
Module
Figure 33: Reference Circuit Design for Headphone Interface

3.22.4. Reference Circuit Design for Loudspeaker Interface

SPK_P EARP
EA
SPK_M
RN
Module
Figure 34: Reference Circuit Design for Loudspeaker Interface

3.22.5. Audio Interfaces Design Considerations

It is recommended to use the electret microphone with dual built-in capacitors (e.g. 10pF and 33pF) for
filtering out RF interference, thus reducing TDD noise. The 33pF capacitor is applied for filtering out RF
interference when the module is transmitting at EGSM900. Without placing this capacitor, TDD noise
could be heard. The 10pF capacitor here is used for filtering out RF interference at DCS1800. Please note
that the resonant frequency point of a capacitor largely depends on the material and production technique.
Therefore, customers would have to discuss with their capacitor vendors to choose the most suitable
SC66_Hardware_Design
R1
0R
F2
F3
F4
C3 C4 C5
D0
0R
33pF 33pF 33pF
R3
F1
F2
C1
C2
33pF
33pF
Smart LTE Module Series
SC66 Hardware Design
1
5
4
3
6
2
D1 D2 D3 D4
D1 D2
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