SimCom SIM548C HD V1.01, Проектирование аппаратного обеспечения

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SIM548C Hardware Design
for microphone. One of the two channels is typically used with a microphone built into a handset.
The other channel is typically used with an external microphone or external line input. The
module analogy input configuration is determined by control register settings and established
using analogy multiplexers.
For each channels, you can use AT+CMIC to set the input gain level of microphone, use
AT+SIDET to set the side-tone level. In addition, you can also use AT+CLVL to adjust the output
gain level of both receiver and speaker at the same time, use AT+CHFA to activate one of the two
audio channels and deactivate the other one.. For more details, please refer to
document [1]
.
Note: Use AT command AT+CHFA to select_audio channel:
0— AIN1/AOUT1 (normal audio channel),
the default value is 0.
1— AIN2/AOUT2(aux_audio channel)
.
It is suggested that you adopt the one of the following two matching circuits in order to improve
audio performance. The difference audio signals have to be layout according to difference signal
layout rules. As show in following figures
(Note: all components package are 0603.)
If you want
to adopt an amplifier circuit for audio, we recommend National company’s LM4890. Of course
you can select it according to your requirement.
Note
：
The GND and AGND should not be connected outside the module.
3.10.1 Speaker interface configuration
Figure 21 : Speaker interface configuration
SIM548C_HD_V1.01 09.05.2008
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