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SIM868_Series_Hardware_Design_V1.06 35 2017-07-13
SPK2N 43 Audio output negative
SPK1P/1N output can directly drive 32Ω receiver.
SPK2P/2N output can directly drive 8Ω speaker, which integrates class-AB audio amplifier as shown Table 14:
Table 14: Performance of audio amplifier
3.3V 8Ω THD+N=1% 0.53W
4.2V 8Ω THD+N=10% 1.08W
3.3V 8Ω THD+N=10% 0.65W
AT command “AT+CMIC” is used to adjust the input gain level of microphone. AT command “AT+SIDET”
is used to set the side-tone level. In addition, AT command “AT+CLVL” is used to adjust the output gain level.
For more details, please refer to document [1].
In order to improve audio performance, the following reference circuits are recommended. The audio signals
have to be layout according to differential signal layout rules as shown in Figure 28 and Figure 29.
5.7.1. Speaker Interfaces Configuration
SPK1P/2P
Close to speaker
ESD
ESD
10pF
33pF
33pF
33pF
Module
SPK1N/2N
10pF
10pF
10pF
33pF
33pF
33pF
10pF
10pF
Figure 28: Speaker reference circuit
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