LISA-U series - System Integration Manual
UBX-13001118 - R17
Advance information
System description
Page 94 of 190
1.11.1.2
Downlink path (differential analog audio output)
The pins related to the differential analog audio output are:
SPK_P / SPK_N
: Differential analog audio signal output (positive/negative). These two pins are internally
directly connected to the differential output of a low power audio amplifier, for which the input is internally
connected to the digital processing system by to an integrated digital-to-analog converter
The analog audio output is selected when the parameter <main_downlink> in AT+USPM command is set to
“Normal earpiece”, “Mono headset” or “Loudspeaker”: the downlink analog path profiles use the same
physical output but have different sets of audio parameters (for more details see the
u-blox AT Commands
Manual
[3], AT+USPM, AT+USGC, AT+UDBF, AT+USTN commands).
The differential analog audio output can be directly connected to a headset earpiece or handset earpiece but is
not able to drive an 8
speaker.
Detailed electrical characteristics of the differential audio output can be found in
LISA-U1 series Data Sheet
Warning: excessive sound pressure from headphones can cause hearing loss.
Table 41 lists the signals related to analog audio functions.
Name
Module
Description
Remarks
MIC_P
LISA-U120
LISA-U130
Differential analog audio input (Positive)
Shared for all uplink analog path modes:
handset, headset, hands-free mode.
Internal DC blocking capacitor.
MIC_N
LISA-U120
LISA-U130
Differential analog audio input (Negative)
Shared for all uplink analog path modes:
handset, headset, hands-free mode.
Internal DC blocking capacitor.
SPK_P
LISA-U120
LISA-U130
Differential analog audio output (Positive)
Shared for all uplink analog path modes:
earpiece, headset, loudspeaker mode.
SPK_N
LISA-U120
LISA-U130
Differential analog audio output (Negative)
Shared for all uplink analog path modes:
earpiece, headset, loudspeaker mode.
Table 41: Analog audio interface pins
The audio pins ESD sensitivity rating is 1 kV (Human Body Model according to JESD22-A114F). Higher
protection level could be required if the lines are externally accessible on the application board. Higher
protection level can be achieved by mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor
array) on the lines connected to these pins, close to accessible points.
All corresponding differential audio lines must be routed in pairs, be embedded in GND (have the ground
lines as close as possible to the audio lines), and maintain distance from noisy lines such as
VCC
and from
components such as switching regulators.
If the audio pins are not used, they can be left unconnected on the application board.
1.11.1.3
Headset mode
Headset mode is the default audio operating mode of the LISA-U120 and LISA-U130 modules. The headset
profile is configured when the uplink audio path is set to “Headset microphone” and the downlink audio path is
set to “Mono headset” (see the
u-blox AT Commands Manual
[3]: AT+USPM command: <main_uplink>,
<main_downlink> parameters):
Headset microphone must be connected to the module differential input
MIC_P / MIC_N
Headset receiver must be connected to the module differential output
SPK_P / SPK_N
