SARA-G450 - System integration manual
UBX-18046432 - R08 Design-in Page 110 of 143
C1-Public
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. The protection should be mounted close to accessible point of the line (D1-D4
parts in the circuit described in Figure 70).
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
C6 C7
L2
L1
C5C4
LSPKLoudspeaker
connector
J2
Microphone
connector
MIC
J1
OUT+
IN+
GND
U1
OUT-
IN-
C8
C9
R5
R6
VDD
C11C10
Audio
amplifier
VCC
D3
D1
D4
D2
Figure 70: 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
47 nF capacitor ceramic X7R 0402 10% 16V
GRM155R71C473KA01 – 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
0 Ω resistor 0402 5% 0.1 W
RC0402JR-070RL – Yageo Phycomp
Filter-less mono 2.8 W class-D audio amplifier
SSM2305CPZ – Analog Devices
Table 44: 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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