User's Manual

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Note d’étude / Technical document : URD1 – 5625.1 – 006 / 69796 Edition 03

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3.2 HOW to connect the AUDIOS?

The MO300 module feature 2 differential audio paths. A main audio path to connect a microphone and a

speaker, and a second one to connect an auxiliary audio through a Jack (for example). In this following chapter

examples of design will be given including protections against EMC and ESD and some notes about the routing

rules to follow to avoid the TDMA noise usually present in this sensitive area of design. It will also give the way

to use the hook function and the audio-jack presence detector.

3.2.1 Using a differential Handset mode on the main audio path

The MO300 can manage an external microphone (MICP/MICN) and external speaker (32 ohms SPKP/SPKN) in

differential mode.

Thus, one receiver and one microphone can be connected to the module with the following characteristics (see

SAGEM references):

- Receiver 32 ohms up to 120 ohms

- Microphone accepting the polarisation described below (FET Buffer + Open Drain).

- The microphone can be supplied using the internal MO300 bias supply (recommended but not mandatory)

or any other external bias system compliant with selected microphone within the MO300 inputs limits.

Figure 13

Differential audio handset mode

Figure 14

Microphone on board components

Protective components

speaker

MO300

SPKP

SPKN

MICP

MICN

2.0V / 2.5V

MICBIAS

47nH

15pF

22pF

15pF

22pF

47nH

Micro

hone

See

Application

schematic