LISA-U2 series - System integration manual
UBX-13001118 - R27
System description
Page 96 of 183
C1-Public
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
describe an application circuit for I2S 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 I2S digital audio interface of the LISA-U2 series modules that acts as an I2S host is connected to
the digital audio interface of the external audio codec (that acts as an I2S local device). The first I2S
interface can be used as well as the second I2S 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 I2S 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 (I2C) 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