Smart Module Series
SC200R&SC262R_Series_Hardware_Design 73 / 124
3.22.3. Reference Circuit Design for Headset Interface
20K
ESD
MIC_GND
MIC2_P
HPH_L
HS_DET
HPH_R
HPH_REF
33 pF
Module
R1
0R
6
3
4
5
2
1
33 pF 33 pF
C3
C4
C5
F3
F2
F1
D1 D2 D3 D4
F4
R2
R3
0R
Figure 26: Reference Circuit Design for Headphone Interface
3.22.4. Reference Circuit Design for Loudspeaker Interface
EARP
EA
RN
F2
SPK_P
SPK_N
33 pF
33 pF
C1
C2
F1
Module
D1
D2
Figure 27: Reference Circuit Design for Loudspeaker Interface
3.22.5. Design Considerations for Audio Interfaces
It is recommended to use the electret microphone with dual built-in capacitors (e.g. 10 pF and 33 pF) to
filter out RF interference, thus reducing TDD noise. The 33 pF capacitor is applied to filter out RF
interference when the module is transmitting at EGSM900. Without this capacitor, TDD noise could be
heard during voice calls. The 10 pF capacitor is used to filter out RF interference at DCS1800. Please
note that the resonant frequency point of a capacitor largely depends on its material and manufacturing