User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information System description
Page 65 of 116
Table 26 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 26: Analog Audio Signal Pins
The audio pins ESD rating is 1 kV (contact discharge). A higher protection level could be required if the
lines are externally accessible on the application board. A higher protection level can be achieved
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) on the lines connected to
these pins.
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” (refer to u-blox AT Commands Manual [2]: 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
Figure 38 shows an example of an application circuit connecting a headset (with a 2.2 k electret microphone
and a 32  receiver) to the LISA-U120 and LISA-U130 modules, with an external low noise LDO voltage
regulator to provide a proper supply for the microphone.
Mount an 82 nH series inductor (e.g. Murata LQG15HS82NJ02) on each microphone line, and a 27 pF
bypass capacitor (e.g. Murata GRM1555C1H270J) on all audio lines to minimize RF coupling and TDMA
noise.
The physical width of the audio outputs lines on the application board must be wide enough to
minimize series resistance.