Huawei MG323 manual Audio Interface, 12External circuit for 32 Ω handsets/16 Ω headsets

HUAWEI MG323 GSM M2M Module
Hardware Guide	Description of the Application Interfaces

To meet the requirements of 3GPP TS 51.010-1 protocols and electromagnetic compatibility (EMC) authentication, the SIM card socket should be placed near the B2B connector interface (it is recommended that the PCB circuit connecting the B2B connector interface and the SIM card socket not exceed 100 mm), because a long circuit may lead to wave distortion, thus affecting signal quality.

It is recommended that you wrap the area adjacent to the SIM_CLK and

SIM_DATA signal wires with a ground wire. The GND pin of the SIM card socket and the GND pin of the SIM card must be well connected to the power GND pin supplying power to the MG323 module.

A 0.1 µF capacitor or a 0.22 µF capacitor is placed between the VSIM and GND pins in parallel. Three 33 pF capacitors are placed respectively between the SIM_DATA and GND pins, the SIM_RST and GND pins, and the SIM_CLK and GND pins in parallel to filter interference from RF signals.

You do not need to pull the SIM_DATA pin up during design as a 15 kΩ resistor is used to connect the SIM_DATA pin to the VSIM pin.

It is recommended to take electrostatic discharge (ESD) protection measures near the SIM card socket. The TVS diode with Vrwm of 5 V and junction capacitance less than 10 pF must be placed as close as possible to the SIM socket, and the Ground pin of the ESD protection component is well connected to the power Ground pin that supplies power to the MG323 module.

3.8Audio Interface

The MG323 module provides two types of audio interfaces: one is for handsets, the other is for headsets. The audio interfaces of the MG323 module support input from handset microphones and headset microphones, and provide output that supports 32

Ωhandsets and 16 Ω headsets. Differential signal lines are recommended for the microphone interface and the speaker interface. Single-ended signal lines are not recommended. The reception gain can be adjusted by using software.

Figure 3-12External circuit for 32 Ω handsets/16 Ω headsets

HUAWEI Module (Modem)

INTEAR_P/	ferrite bead
EXTEAR_P			100 pF
INTEAR_N/	ferrite bead
EXTEAR_N
	33 pF	33 pF

ESD protection

+

-

Speaker

Issue 06 (2013-06-13)	Huawei Proprietary and Confidential	27
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