Integration Manual

LISA-U2 series - System Integration Manual
UBX-13001118 - R25 System description Page 96 of 182
Examples of manufacturers offering compatible audio codec parts, suitable to provide basic analog
audio voice capability on the application device, are the following:
 Maxim Integrated (as the MAX9860, MAX9867, MAX9880A audio codecs)
 Texas Instruments / National Semiconductor
 Cirrus Logic / Wolfson Microelectronics
 Nuvoton Technology
 Asahi Kasei Microdevices
 Realtek Semiconductor
Figure 50 and Table 41 describe an application circuit for I
2
S digital audio interfaces of LISA-U2 series
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.
An I
2
S digital audio interface of the LISA-U2 series modules that acts as an I
2
S master is connected
to the digital audio interface of the external audio codec (that acts as an I
2
S slave). The first I
2
S
interface can be used as well as the second I
2
S interface of the cellular module.
The CODEC_CLK digital output clock of the cellular module is connected to the clock input of the
external audio codec to provide the clock reference.
Signal integrity of the high speed lines may be degraded if the PCB layout is not optimal, especially
when the CODEC_CLK clock line or also the I
2
S digital audio interface lines are very long: keep routing
short and minimize parasitic capacitance to preserve signal integrity.
The external audio codec is controlled by the cellular module using the DDC (I
2
C) interface: this
interface can be used to communicate with u-blox GNSS receivers and at the same time to control an
external audio codec on all LISA-U2 series modules.
The V_INT supply output of the cellular module provides the supply to the external audio codec,
defining a suitable voltage level for the digital interfaces.
Additional components are provided for EMC and ESD immunity conformity according to European
Norms for Radio Equipment Directive (2014/53/EU) and EMC Directive (2014/30/EU) compliance. The
recommended parts for EMC and ESD immunity conformity are: a 10 nF bypass capacitor (e.g. Murata
GRM155R71C103KA88) and a proper series chip ferrite bead noise/EMI suppression filter (e.g. Murata
BLM15HD182SN1) provided on each microphone line input and speaker line output of the external
codec as illustrated in Figure 50 and Table 41.
53
I2S1_CLK
54
I2S1_WA
R2R1
BCLK
GND
U1
LRCLK
LISA-U2 series
Audio
Codec
40
I2S1_TXD
39
I2S1_RXD
SDIN
SDOUT
46
SDA
45
SCL
SDA
SCL
52
CODEC_CLK
MCLK
GND
IRQn
R3
C3C2
C1
4
V_INT
VDD
1V8
MICBIAS
C4
R4
C5
C6
EMI1
MICLN
MICLP
D1
Microphone
Connector
EMI2
MIC
C12 C11
J1
MICGND
R5
C8 C7
D2
SPK
Speaker
Connector
OUTP
OUTN
J2
C10 C9C14 C13
EMI
3
EMI
4
Figure 50: I
2
S interface application circuit with an external audio codec to provide voice capability