Hardware Design - Rainbow Technologies

SIM300DZ Hardware Design3.10 Audio interfacesTable 13: Audio interface signalName Pin Function(AIN1/AOUT1)(AIN2/AOUT2)MIC1P 20 Microphone1 input +MIC1N 21 Microphone1 input -SPK1P 23 Audio1 output+SPK1N 24 Audio1 output-MIC2P 18 Microphone2 input +MIC2N 19 Microphone2 input -SPK2P 26 Audio2 output+SPK2N 25 Audio2 output-The module provides two analogy input channels, AIN1 and AIN2, which may be used for bothmicrophone and line inputs. The AIN1 and AIN2 channels are identical. One of the two channelsis typically used with a microphone built into a handset. The other channel is typically used withan external microphone or external line input. The module analogy input configuration isdetermined 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, useAT+ECHO to set the parameters for echo cancellation. Also, you can use AT+SIDET to set theside-tone level. For detail, please refer to document [1].It is suggested that you adopt the one of following two matching circuits in order to rejectcommon mode noise and audio noise. The difference audio signals have to be layout according todifference signal layout rules.Notes:As show in following Figures (Note : all components package are 0603) .BEAD must has lowimpedance and can be removed according to their environment such as the ground plane,shielding, power lost. The best way is to plan all the components shown in the follow figure. Ifyou want to adopt an amplifier circuit for audio, we commend National company’s LM4890.But you can select it according to your needs.SIM300DZ_HD_V2.03 3810.01.2007