Specifications

Product Technical Specification & Customer Design Guidelines
Interfaces
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This document is the sole and exclusive property of WAVECOM. Not to be distributed or divulged without
prior written agreement.
WA_DEV_Q64_PTS_001-003 January 9, 2009
3.11 Analogue Audio Interface
Two different microphone inputs and two different speaker outputs are supported.
Audio 1 (MIC and EAR) is designed for handset type application and auxiliary audio is
designed for car-kit type application.
The Q64 also includes an echo cancellation feature which allows hands-free function.
In some cases, ESD protection must be added on the audio interface lines.
3.11.1 Microphone Features
Audio 1 can be configured in differential or single ended, while auxiliary audio can
only be configured in single ended.
In audio 1, 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. Either in audio 1 or auxiliary audio, when using a single-
ended connection, make sure to have a very good ground plane, a very good filtering
as well as shielding in order to avoid any disturbance on the audio path. It is
recommended to use the Q64 Wireless CPU
®
AREF pin for the good plane connection.
The gain of MIC inputs is internally adjusted and can be tuned using an AT
command.
3.11.1.1 Electrical Characteristics
3.11.1.1.1 MIC1 Microphone Inputs
By default, the MIC1 inputs are differential ones, but they can be configured in single
ended mode. They already include the convenient biasing for an electret microphone.
The electret microphone can be directly connected on those inputs, thus allowing
easy connection to a handset.
AC coupling is already embedded in the Wireless CPU
®
.
Equivalent circuits of MIC1
DC equivalent circuit AC equivalent circuit
MIC1P
MIC1N
Z1
Z1
GND
MIC1+
MIC1P
MIC1N
R
R
GND