Rainbow Electronics MG260 - Manual (Page 43)

MG260 Product Specification
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2.6.6 Audio interface
Two different microphone inputs (MIC1 and MIC2) and two different speaker outputs
(SPK1 and SPK2) are supported.
Main audio interface is made up of MIC2 inputs (microphone) and SPK2 outputs
(speaker).
Auxiliary audio interface is made up of MIC1 inputs (microphone) and SPK1
outputs (SPK1). Auxiliary audio interface is appropriate for a hands-free system or a
handset with biasing external to the module.
The MG260 module also includes echo cancellation and noise reduction features
improving quality of hands-free function.
In some cases, ESD protection must be added on the audio interface lines.
2.6.6.1 Microphone inputs
2.6.6.1.1 General description
The main microphone inputs (MIC2) already include the biasing for an electret
microphone allowing an easy connection to a handset.
The auxiliary microphone inputs (MIC1) do not include an internal bias.
For both microphone paths the connection can be either differential or single-
ended but using a differential connection in order to reject common mode
noise and TDMA noise is strongly recommended.
The use of a single-ended connection requires a very good ground plane, a
very good filtering as well as shielding in order to avoid any disturbance on
the audio path.
2.6.6.1.2 Main Microphone Inputs (MIC2)
MIC2 inputs include an internal convenient biasing for an electret microphone.
This electret microphone can be directly connected on these inputs, either in
differential or single-ended mode.
The gain is internally adjusted through AT commands.
AC coupling is already embedded in the module.
Pin description
Signal Pin # I/O I/O type Description
MIC2P 66 I Analog Microphone 2 positive input
MIC2N 68 I Analog Microphone 2 negative input