User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information System description
Page 67 of 116
LISA-U120/U130
C1 C2 C3
J1
4
3
2
1
L1
53
SPK_P
54
SPK_N
40
MIC_P
39
MIC_N
D1
AUDIO
HANDSET
CONNECTOR
D2
INOUT
GND
Low Noise
LDO Regulator
U1
R4
R1
C6
R3R2
C5
2V5
Sense lines connected to GND in one star point
C4
L2
VMAIN
C7
Figure 39: Handset mode application circuit
Reference
Description
Part Number - Manufacturer
C1, C2, C3, C4
27 pF Capacitor Ceramic COG 0402 5% 25 V
GRM1555C1H270JA01 - Murata
C5, C6, C7
10 µF Capacitor Ceramic X5R 0603 20% 6.3 V
GRM188R60J106ME47 - Murata
D1, D2
Low Capacitance ESD Protection
USB0002RP or USB0002DP - AVX
L1, L2
82nH Multilayer inductor 0402
(self resonance frequency ~1 GHz)
LQG15HS82NJ02 - Murata
J1
Audio Handset Jack Connector, 4Ckt (4P4C)
52018-4416 - Molex
R1, R2, R3, R4
2.2 kΩ Resistor 0402 5% 0.1 W
RC0402JR-072K2L - Yageo Phycomp
U1
Low Noise LDO Linear Regulator 2.5 V 300 mA
LT1962EMS8-2.5#PBF- Linear Technology
Table 28: Example of components for handset connection
1.11.1.5 Hands-free mode
The hands-free profile is configured when the uplink audio path is set to “Hands-free microphone” and the
downlink audio path is set to “Loudspeaker” (refer to u-blox AT commands manual [2]: AT+USPM command:
<main_uplink>, <main_downlink> parameters):
 Hands-free microphone signal must be connected to the module differential input MIC_P / MIC_N
 High power loudspeaker must be connected to the output of an external audio amplifier, for which the
input must be connected to the module differential output SPK_P / SPK_N
The module differential analog audio output is not able to drive an 8  speaker: an external audio amplifier
must be provided on the application board to amplify the low power audio signal provided by the module
differential output SPK_P / SPK_N.
Hands-free functionality is implemented using appropriate digital signal processing algorithms for voice-band
handling (echo canceller and automatic gain control), managed via software (refer to u-blox AT commands
manual [2], AT+UHFP command).
Figure 39 shows an example of an application circuit connecting a 2.2 k electret microphone and an 8 
speaker to the LISA-U120 and LISA-U130 modules, with an external low noise LDO voltage regulator to provide
a proper supply for the microphone and with an external audio amplifier to amplify the low power audio signal
provided by the module differential output.