u-blox LEON-G100 ECALL, System Integration Manual

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LEON-G100 / LEON-G200 - System Integration Manual
GSM.G1-HW-09002-G3 Preliminary System description
Page 64 of 125
The default parameters for audio uplink profiles “Handset microphone” and “Headset microphone”
(refer to
u-blox AT Commands Manual [2]; AT+UMGC, AT+UUBF, AT+UHFP) are for a handset and a
headset microphone. To implement hands-free mode, these parameters should be changed on the
audio path corresponding to the connection chosen. Procedure to tune parameters for hands-free mode
(gains, echo canceller) can be found in
LEON Audio Application Note [12].
When hands-free mode is enabled, the audio output signal on
HS_P is disabled.
The physical width of the high-power audio outputs lines on the application board must be wide
enough to minimize series resistance.
Figure 38 shows an application circuit for hands-free mode. In this example the LEON-G100 / LEON-G200
modules are connected to an 8
Ω speaker and a 2.2 k Ω electret microphone. Insert 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 the TDMA noise.
LEON-G100 /
LEON-G200
SPK
C1 C2
L2
L1
MIC
C3 C4
39
SPK_N
38 SPK_P
43
MIC_GND1
44 MIC_BIAS1
Figure 38: Hands free mode application circuit
Reference Description Part Number - Manufacturer
C1, C2, C3, C4 27 pF Capacitor Ceramic COG 0402 5% 25 V GRM1555C1H270JZ01 - Murata
L1, L2 82nH Multilayer inductor 0402
(self resonance frequency ~1 GHz) LQG15HS82NJ02 - Murata
SPK Loudspeaker
MIC Active Elected Microphone
Table 24: Example of components for hands-free connection
1.10.1.6 Connection to an external analog audio device
MIC_BIAS1 / MIC_GND single ended analog audio inputs and the HS_P single ended analog audio output of
LEON-G100 / LEON-G200 can be used to connect the module to an external analog audio device.
If the external analog audio device is provided with a single ended analog audio input, the
HS_P single ended
output of the module must be connected to the single ended input of the external audio device by a DC-block
10 µF series capacitor (e.g. Murata GRM188R60J106M) to decouple the bias present at the module output (see
HS_P common mode output voltage in LEON-G100 / LEON-G200 Data Sheet [1]). Use a suitable power-on
sequence to avoid audio bump due to charging of the capacitor: the final audio stage should always be the last
one enabled.
If the external analog audio device is provided with a differential analog audio input, a proper single ended to
differential circuit must be inserted from the
HS_P
single ended output of the module to the differential input of
the external audio device. A simple application circuit is described in Figure 39: a DC-block 10 µF series capacitor