LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
System description
Page 68 of 125
MIC_P / MIC_N
: Differential analog audio signal inputs (positive/negative). These two pins are provided with
internal series 100 nF capacitors for DC blocking that connect the module pads to the differential input of a
Low Noise Amplifier. The LNA output is internally connected to the digital processing system by an
integrated sigma-delta analog-to-digital converter
The analog audio input is selected when the parameter <main_uplink> in AT+USPM command is set to
“Headset microphone”, “Handset microphone” or “Hands-free microphone”: the uplink analog path profiles
use the same physical input but have different sets of audio parameters (for more details please refer to
u-blox
[2], AT+USPM, AT+UMGC, AT+UUBF, AT+UHFP commands).
There is no microphone supply pin available on the module: an external low noise LDO voltage regulator should
be added to provide a proper supply for a microphone.
Detailed electrical characteristics of the differential analog audio input can be found in the
LISA-U1 series
Data
1.11.1.2
Downlink path (differential analog audio output)
The pins related to the differential analog audio output are:
SPK_N / SPK_P
: 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 please refer to
u-blox AT
[2], 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 the
LISA-U1 series Data Sheet
Warning: excessive sound pressure from headphones can cause hearing loss.
Table 27 lists the signals related to analog audio functions.
Name
Description
Remarks
MIC_P
Differential analog audio input (Positive)
Shared for all uplink analog path modes: handset, headset,
hands-free mode.
Internal DC blocking capacitor.
MIC_N
Differential analog audio input (Negative)
Shared for all uplink analog path modes: handset, headset,
hands-free mode.
Internal DC blocking capacitor.
SPK_P
Differential analog audio output (Positive)
Shared for all uplink analog path modes: earpiece, headset,
loudspeaker mode.
SPK_N
Differential analog audio output (Negative)
Shared for all uplink analog path modes: earpiece, headset,
loudspeaker mode.
Table 27: Analog Audio Signal 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.
