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SIM800L(MT6261)_Hardware Design_V1.01 34 2016-07-07
SPK1P/1N output can directly drive 32Ω receiver, SIM800L internal has class-AB audio amplifier, the following
table is class-AB performance:
Table 14: Performance of audio amplifier
4.2V 8Ω THD+N=1% 0.87W
3.4V 8Ω THD+N=1% 0.53W
4.2V 8Ω THD+N=10% 1.08W
3.4V 8Ω THD+N=10% 0.65W
SPK2P/2N output can directly drive 8Ω speaker.
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 following figures.
4.7.1. 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 30: Speaker reference circuit
SPK1P 53 Main Audio output positive
SPK1N 13 Main Audio output negative
Secondary
MIC2P 9 Secondary Audio input positive
MIC2N 10 Secondary Audio input negative
SPK2P 51 Secondary Audio output positive
Secondary Audio output negative
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