User's Manual

MC703 CDMA EV-DO Wireless Module
Product Description
Issue 1.00 (2009-08-24) Huawei Proprietary and Confidential Page 23 of 45
Figure 3-3 Reset process of the MC703 CDMA EV-DO module
The RESET_N pin is sensitive to interference. Therefore, the lines on the interface board of the MC703
CDMA EV-DO module should be not longer than 2 cm. Otherwise, the MC703 CDMA EV-DO module
may be reset because of interference.
3.5.4 RTC Power Supply
The power supply pin for the real-time clock (RTC) can obtain current from the VBAT pin
through software enabling to charge the backup battery of the RTC. The power supply input is
monitored by a CPU.
The MC703 CDMA EV-DO module defines the VCOIN pin for the input of the backup power
supply on the 60-pin B2B connector to implement the power supply input for the RTC.
Table 3-7 VCOIN pin for the input of the RTC power supply
PIN Name I/O Function Remarks
12 VCOIN P Input of the backup power
supply
This pin is connected to a button-type
battery or a capacitor of large
capacitance.
If the RTC backup battery is not used, you can connect the pin to the primary power supply,
or use an electrolytic capacitor of large capacitance.
Table 3-8 Parameters of the RTC power supply pin