Huawei Technologies Co. Ltd UM01-HW Manuel D’Utilisation

   

MC703 CDMA EV-DO Wireless Module V100R001

Product Description

 

Issue 1.00 (2009-9-10) 

Huawei Proprietary and Confidential

Page 31 of 40

 

Figure 4-6 Circuits of the first audio interface 

 

Differential signals are transmitted on the first audio interface. By reserving a place for the 
resistor in the loop, you can adjust the quality and volume of the voice. It is recommended 
that you place a TVS on the related interface to provide protection against ESD and protect 
components such as the internal integrated circuit (IC) component. 

The output signals of the second audio interface can directly drive an 8-ohm speaker. 

Figure 4-7 Connections between the UM01-HW UMTS module and the 8-ohm speaker 

 

 

An external power supply with the voltage of 3.3 V to 4.2 V (the typical value is 3.8 V) 
powers the UM01-HW UMTS module through the VBAT pin. When the network signals are 
weak, the antenna transmits signals with the highest power and the maximum transient current 
is up to 1.6 A. In this case, it is recommended that you use a low dropout (LDO) regulator or a 
switching-mode power supply whose current is higher than 1.6 A.   

Considering the voltage drop that may occur during the transmission with high power, you 
can add a large capacitor on the power supply interface of the module. The electrolytic 
capacitor of over 220 µF is recommended.