Decrease Tdd Noise And Other Noise - Quectel UC15 Hardware Design

AOUT1
MIC1N
SPK1P
SPK1N
MIC2P
MIC2N
AIN2/
AOUT2
SPK2P
AGND

AIN1 and AIN2 may be used for both microphone and line inputs. An electret microphone is usually
recommended. AIN1 and AIN2 are both differential input channels.

AOUT1 and AOUT2 may be used for both receiver and speaker outputs. AOUT1 channel is typically
used for a receiver, while AOUT2 channel is typically used for headset or speaker. AOUT1 channel is
a differential channel and AOUT2 is a single-ended channel. SPK2P and AGND can establish a
pseudo differential mode. Both AOUT1 and AOUT2 support voice and ringtone output, and so on.

These two audio channels can be swapped by AT+QAUDPATH command. For more details, please
refer to document [1].
Use command AT+QAUDPATH to select audio channel:
0: AIN1/AOUT1 (normal audio channel), the default value is 0.
1: AIN2/AOUT2 (auxiliary audio channel).
2: PCM channel.
For each channel, you can use AT+QMIC to adjust the input gain level of microphone. You can also use
AT+CLVL to adjust the output gain level of receiver and speaker. AT+QSIDET is to set the side-tone gain
level. For more details, please refer to document [1].
3.11.1.

Decrease TDD Noise and Other Noise

The 33pF capacitor is applied for filtering out 900MHz RF interference when the module is transmitting at
GSM900/EGSM900MHz. TDD noise could be heard without this capacitor. Moreover, the 10pF capacitor
here is for filtering out 1800/1900MHz RF interference. However, the self-resonant frequency point of a
capacitor largely depends on the material and production technique. Therefore, customer should depend
on its capacitor vendor to choose the most suitable capacitor for filtering out GSM850MHz,
EGSM900MHz, DCS1800MHz and PCS1900MHz separately.
UC15_Hardware_Design
24 AI Audio negative input.
22 AO Audio positive output.
21 AO Audio negative output.
Auxiliary audio positive
25 AI
input.
Auxiliary audio negative
26 AI
input.
Auxiliary audio positive
20 AO
output.
19 Analog ground.
Confidential / Released
UMTS/HSDPA Module Series
UC15 Hardware Design
If it is unused, keep open.
If it is unused, keep open.
If it is unused, keep open.
If it is unused, keep open.
If it is unused, keep open.
If it is unused, keep open.
Suggested to be used for
audio circuit.
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