Ublox SARA-G300 - Page 157

SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R26 Design-in
Page 157 of 217
Figure 86 and Table 57 describe an application circuit example for the I
2
S digital audio interface of SARA-U2
modules providing voice capability using an external audio voice codec. DAC and ADC integrated in the external
audio codec respectively converts an incoming digital data stream to analog audio output through a mono
amplifier and converts the microphone input signal to the digital bit stream over the digital audio interface.
 The module’s I
2
S interface (I
2
S master) is connected to the related pins of the external audio codec (I
2
S slave).
 The V_INT output supplies the external audio codec, defining proper digital interfaces voltage level.
 The external audio codec is controlled by the SARA-U2 module using the DDC (I
2
C) interface: this interface
can be concurrently used to communicate with u-blox GNSS receivers and with an external audio codec.
 The CODEC_CLK pin of the SARA-U2 module (that provides a suitable digital output clock) is connected to
the clock input of the external audio codec to provide clock reference.
 Additional components are provided for EMC and ESD immunity conformity: a 10 nF bypass capacitor and a
series chip ferrite bead noise/EMI suppression filter provided on each microphone line input and speaker line
output of the external codec as described in Figure 86 and Table 57. The necessity of these or other
additional parts for EMC improvement may depend on the specific application board design.
R2R1
GND
U1
SARA-U2 series
Audio
Codec
26
SDA
27
SCL
SDA
SCL
19
CODEC_CLK
MCLK
GND
R3
C3C2
C1
4
V_INT
VDD
1V8
MICBIAS
C4
R4
C5
C6
EMI1
MICLN
MICLP
Microphone
Connector
EMI2
MIC
C12 C11
J1
MICGND
R5
C8 C7
SPK
Speaker
Connector
OUTP
OUTN
J2
C10 C9C14 C13
EMI3
EMI4
IRQn
BCLK
LRCLK
SDIN
SDOUT
36
I2S_CLK
34
I2S_WA
35
I2S_TXD
37
I2S_RXD
1V81V8
D3
D1
D4
D2
Figure 86: Application circuit for connecting SARA-U2 modules with an external audio codec to provide voice capability
Reference
Description
Part Number – Manufacturer
C1
100 nF Capacitor Ceramic X5R 0402 10% 10V
GRM155R71C104KA01 – Murata
C2, C4, C5, C6
1 µF Capacitor Ceramic X5R 0402 10% 6.3 V
GRM155R60J105KE19 – Murata
C3
10 µF Capacitor Ceramic X5R 0603 20% 6.3 V
GRM188R60J106ME47 – Murata
C7, C8, C9, C10
27 pF Capacitor Ceramic COG 0402 5% 25 V
GRM1555C1H270JZ01 – Murata
C11, C12, C13, C14
10 nF Capacitor Ceramic X5R 0402 10% 50V
GRM155R71C103KA88 – Murata
D1, D2, D3, D4
Low Capacitance ESD Protection
CG0402MLE-18G – Bourns
EMI1, EMI2, EMI3,
EMI4
Chip Ferrite Bead Noise/EMI Suppression Filter
1800 Ohm at 100 MHz, 2700 Ohm at 1 GHz
BLM15HD182SN1 – Murata
J1
Microphone Connector
Various manufacturers
J2
Speaker Connector
Various manufacturers
MIC
2.2 k Electret Microphone
Various manufacturers
R1, R2
4.7 kΩ Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
R3
10 kΩ Resistor 0402 5% 0.1 W
RC0402JR-0710KL - Yageo Phycomp
R4, R5
2.2 kΩ Resistor 0402 5% 0.1 W
RC0402JR-072K2L – Yageo Phycomp
SPK
32  Speaker
Various manufacturers
U1
16-Bit Mono Audio Voice Codec
MAX9860ETG+ - Maxim
Table 57: Example of components for connecting SARA-U2 modules with an external audio codec to provide voice capability