u-blox SARA-G3 Series System Integration Manual page 141

Mount a 27 pF bypass capacitor (e.g. Murata GRM1555C1H270J) from each microphone
o
line to solid ground plane (C4 and C5 capacitors in

Use a microphone designed for GSM applications, which typically has an internal built-in bypass
capacitor.
 Connect the SPK_P and SPK_N analog downlink outputs directly to the receiver / speaker (which
resistance rating must be greater than 14 ).
 Provide proper parts on each line connected to the receiver / speaker as noise and EMI improvments,
to minimize RF coupling, according to EMC requirements of the custom application.
Mount a 27 pF bypass capacitor (e.g. Murata GRM1555C1H270J) from each speaker line to
o
solid ground plane (C6 and C7 capacitors in
 Provide additional ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) 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 an accessible point of the line (D1 and D2 in
Figure 57Figure 57).
SARA-G350
M IC_BIAS
46
R1
C2
M IC_P
49
C3
M IC_N
48
M IC_GND
47
SPK_P
44
SPK_N 45
Figure 57: Analog audio interface headset and handset mode application circuit
Reference Description
C1 10 µF Capacitor Ceramic X5R 0603 20% 6.3 V
C2, C3 100 nF Capacitor Ceramic X7R 0402 10% 16 V
C4, C5, C6, C7 27 pF Capacitor Ceramic C0G 0402 5% 25 V
D1, D2 Low Capacitance ESD Protection
J1 Microphone Connector
J2 Speaker Connector
UBX-13000995 - R06
SARA-G3 series - System Integration Manual
Figure 57Figure
C1
R2 R4
L1
R3
L2
C4 C5
C6 C7
Part Number – Manufacturer
GRM188R60J106ME47 – Murata
GRM155R71C104KA88 – Murata
GRM1555C1H270JA01 – Murata
USB0002RP or USB0002DP – AVX
Various Manufacturers
Various Manufacturers
Objective Specification
Figure 57Figure 57).
57).
Microphone
MIC
Connector
J1
D1
Speaker SPK
Connector
J2
D2
Page 141 of 218
Formatted: English (U.S.)
Formatted: English (U.S.)
Design-in