Audio Interfaces; Speaker Interfaces Configuration - SIM Tech SIMCom SIM800C Hardware Design

4.7. Audio Interfaces

SIM800C provides an analog input (MICP; MICN), which could be used for electret microphone. The module
also provides an analog output (SPKP; SPKN).
Table 12: Audio interface definition
Pin name Pin number
MICP 9
MICN 10
SPKP 11
SPKN 12
SPKP/SPKN output can directly drive 32Ω receiver, SIM800C internal has class-AB audio amplifier, the
following table is class-AB performance:
Table 13: Performance of audio amplifier
Conditions
4.2V 8Ω THD+N=1%
3.4V 8Ω THD+N=1%
4.2V 8Ω THD+N=10%
3.4V 8Ω THD+N=10%
SPKP/SPKN 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

SIM800C_Hardware_Design_V1.00
Figure 28: UART1_RI behaviour as a caller
Function
Audio input positive
Audio input negative
Audio output positive
Audio output negative
Class-AB AMP
0.87W
0.53W
1.08W
0.65W
31
Smart Machine Smart Decision
2014-10-30