Output Power Supply Interface - Huawei ME909u-521 Hardware Manual

HUAWEI ME909u-521 LTE LGA Module
Hardware Guide
When the ME909u-521 module is used for different external applications, pay special
attention to the design for the power supply. When the ME909u-521 module works at
2G mode and transmits signals at the maximum power, the transient current may
reach the transient peak value of about 2.5 A due to the differences in actual network
environments. In this case, the VBAT voltage drops. If you want wireless good
performance, please make sure that the voltage does not decrease below 3.3 V in any
case. Otherwise, exceptions such as restart of the ME909u-521 module may occur.
A low-dropout (LDO) regulator or switch power with current output of more than 2.5 A
is recommended for external power supply. Furthermore, five 220 µF or above energy
storage capacitors are connected in parallel at the power interface of the ME909u-521
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 customers add the EMI ferrite bead (FBMJ1608HS280NT
manufactured by TAIYO YUDEN or MPZ1608S300ATAH0 manufactured by TDK is
recommended) to directly isolate DTE from DCE in the power circuit. Figure 3-3
shows the recommended power circuit of ME909u-521 module.
Figure 3-3 Recommended power circuit of ME909u-521 module
When the system power restarts, a discharge circuit is recommended to make sure
the power voltage drops below 1.8 V and stays for 100 ms at least. This is very
important. If POWER_ON_OFF is asserted when the VBAT is between 1.8 V to 3.2 V,
the module may enter an unexpected status.

3.3.3 Output Power Supply Interface

Output power supply interfaces are VCC_EXT1 and USIM_VCC.
Through VCC_EXT1, the ME909u-521 module can supply 1.8 V power externally with
an output current of 10 mA (typical value) for external level conversion or other
applications.
If the ME909u-521 module is in sleep mode, the output power supply interface is in
the low power consumption state (< 500 μA). If the ME909u-521 module is in power
down mode, the output power supply is in the disabled state.
Through the USIM_VCC power supply interface, the ME909u-521 module can supply
1.8 V or 2.85 V power to USIM card. Please pay attention that the transient current
can reach 200 mA.
Issue 05 (2017-12-15)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
Description of the Application Interfaces
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