SARA-G450 - System integration manual
UBX-18046432 - R08 Design-in Page 108 of 143
C1-Public
Provide suitable parts on each line connected to the receiver / speaker as noise and EMI
improvements, to minimize RF coupling, according to the 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 69).
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 EMC/ESD requirements of the
custom application. Mount the protection close to accessible point of the line (D1-D4 in Figure 69).
SARA-G450
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
C5
C4
SPK
Speaker
connector
J2
Microphone
connector
MIC
J1
D4
D2
Figure 69: Analog audio interface 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 43: Examples of components for analog audio interface 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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