Vcoin Interface - Huawei MU509 Series Hardware Manual

HUAWEI MU509 Series HSDPA LGA Module
Hardware Guide
A low-dropout (LDO) regulator or switch power with current output of more than 3 A is
recommended for external power supply. Furthermore, at least five 220 µF storage
capacitors are connected in parallel at the power interface of the MU509 module. In
addition, to reduce the impact of channel impedance on voltage drop, you are
recommended to try to shorten the power supply circuit of the VBAT interface.
It is recommended that add the EMI ferrite bead (NR3015T4R7M manufactured by
TAIYO YUDEN or VLS3015T-4R7MR99 manufactured by TDK is recommended) to
directly isolate DTE from DCE in the power circuit. Figure 3-2 shows the
recommended power circuit of MU509 module.
Figure 3-2 Recommended power circuit of MU509 module

3.3.4 VCOIN Interface

VCOIN pin of MU509 module is used as an analog input from the 3 V coin cell for
Sudden Momentary Power Loss (SMPL), Real-time Clock (RTC) and External Crystal
Oscillator (XTAL) keep-alive power. A capacitor (rather than a coin cell) can be used if
only SMPL is supported (not RTC or XTAL). VCOIN pin is also used as an analog
output for a coin cell or a capacitor charging.
Sudden momentary power loss
If the monitored VBAT drops out-of-range (< 2.55 V nominal), the SMPL feature
initiates a power-on sequence without software intervention, and then VBAT returns
in-range within a programmable interval of between 0.5 and 2.0 seconds. SMPL
achieves immediate and automatic recovery from momentary power loss. A valid
voltage on VCOIN is required to run the SMPL timer. If a capacitor is used instead of a
coin, it must be connected between VCOIN and the ground. The capacitor must be
charged to operate properly as the SMPL power source. The capacitor value depends
on the SMPL timer setting.
Issue 09 (2014-03-06)
Module
(DCE)
VBAT
10 μF
100 nF
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
Description of the Application Interfaces
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+ +
220 μF 220 μF 220 μF
220 μF
VBAT
+
+
220 μF
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