SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R26 Design-in
Page 150 of 217
Provide proper parts on each line connected to the receiver / speaker as noise and EMI improvements, to
minimize RF coupling, according to EMC requirements of the custom application.
o Mount a 27 pF bypass capacitor (e.g. Murata GRM1555C1H270J) from each speaker line to solid
ground plane (C6 and C7 capacitors in Figure 83).
Provide additional ESD protection (e.g. Bourns CG0402MLE-18G varistor) if the analog audio lines will be
externally accessible on the application device, according to the EMC/ESD requirements of the custom
application. Mount the protection close to an accessible point of the line (D1-D4 in Figure 83).
SARA-G340
SARA-G350
49
MIC_P
R1
R2 R4
44
SPK_P
48
MIC_N
45
SPK_N
R3
C1
46
MIC_BIAS
47
MIC_GND
C2
C3
D3
D1
C6 C7
L2
L1
C5C4
SPK
Speaker
Connector
J2
Microphone
Connector
MIC
J1
D4
D2
Figure 83: Analog audio interface headset and handset mode application circuit
Part Number – Manufacturer
10 µF Capacitor Ceramic X5R 0603 20% 6.3 V
GRM188R60J106ME47 – Murata
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C104KA88 – Murata
27 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1H270JA01 – Murata
Low Capacitance ESD Protection
82 nH Multilayer inductor 0402
(self resonance frequency ~1 GHz)
2.2 kΩ Electret Microphone
2.2 kΩ Resistor 0402 5% 0.1 W
RC0402JR-072K2L – Yageo Phycomp
Table 54: Example of components for analog audio interface headset and handset mode application circuit
If the analog audio interface is not used, the analog audio pins (MIC_BIAS, MIC_GND, MIC_P, MIC_N,
SPK_P, SPK_N) can be left unconnected on the application board.
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