LISA-U series - System Integration Manual
UBX-13001118 - R17
Advance information
System description
Page 95 of 190
Figure 51 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.
LISA-U120
LISA-U130
C2
C3
C4
J1
2
5
3
4
6
1
L2
54
SPK_N
53
SPK_P
39
MIC_N
40
MIC_P
D1
AUDIO HEADSET
CONNECTOR
D2
IN
OUT
GND
Low Noise
LDO Regulator
VMAIN
U1
R4
R1
C6
R3
R2
C5
2V5
Sense lines connected to GND in one star point
L1
C1
C7
Figure 51: Headset 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
82 nH Multilayer inductor 0402
(self resonance frequency ~1 GHz)
LQG15HS82NJ02 – Murata
J1
Audio Headset 2.5 mm Jack Connector
SJ1-42535TS-SMT – CUI, Inc.
R1, R2, R3, R4
2.2 k
Ω
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 42: Example of components for headset jack connection
1.11.1.4
Handset mode
The handset profile is configured when the uplink audio path is set to “Handset microphone” and the downlink
audio path is set to “Normal earpiece” (see the
u-blox
AT commands manual
[3]: AT+USPM command:
<main_uplink>, <main_downlink> parameters):
Handset microphone must be connected to the module differential input
MIC_P / MIC_N
Handset receiver must be connected to the module differential output
SPK_P / SPK_N
