LEON-G100 / LEON-G200 - System Integration Manual
GSM.G1-HW-09002-G3
Preliminary
System description
Page 65 of 125
(e.g. Murata GRM188R60J106M) is provided to decouple the bias present at the module output. A voltage
divider is provided to correctly adapt the signal level from the module output to the external audio device input.
The DC-block series capacitor acts as high-pass filter for audio signals, with cut-off frequency depending on both
the values of capacitor and on the input impedance of the audio device. For example: in case of a single ended
connection to 600
external device, the 10 µF capacitor will set the -3 dB cut-off frequency to 103 Hz. The
high-pass filter has a low enough cut-off to not impact the audio signal frequency response.
If the external analog audio device is provided with a single ended analog audio output, the
MIC_BIAS1
single
ended input of the module must be connected to the single ended output 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
input (see
MIC_BIAS1
microphone supply characteristics in
LEON-G100 / LEON-G200
Data Sheet
If the external analog audio device is provided with a differential analog audio output, a proper differential to
single ended circuit must be inserted from the differential output of the external audio device to the
MIC_BIAS1
single ended input of the module. Figure 39 describes a simple application circuit: a DC-block 10 µF series
capacitor (e.g. Murata GRM188R60J106M) is provided to decouple the bias present at the module input, and a
voltage divider is provided to correctly adapt the signal level from the external audio device output to the
module input.
Use a suitable power-on sequence to avoid audio bump due to capacitor charging: the final audio stage should
always be the last one enabled.
Additional circuitry should be inserted depending on the external audio device characteristics.
To enable the audio path corresponding to these input/output, refer to
u-blox AT Commands Manual
AT+USPM command.
To tune audio levels for the external device refer to
u-blox AT Commands Manual
[2], AT+USGC, AT+UMGC
commands.
LEON-G100 /
LEON-G200
C1
37
HS_P
43
MIC_GND1
44
MIC_BIAS1
GND
Analog IN
Analog OUT
Audio Device
Reference
Reference
LEON-G100 /
LEON-G200
37
HS_P
43
MIC_GND1
44
MIC_BIAS1
GND
Positive Analog IN
Audio Device
Negative Analog OUT
Negative Analog IN
Positive Analog OUT
C3
R2
R1
R4
R3
C2
C4
Figure 39: Application circuits to connect the module to audio devices with proper single-ended or differential input/output
