Huawei ME909u-521 Hardware Manual page 30

HUAWEI ME909u-521 LTE LGA Module
Hardware Guide
Pull up resistor is never needed for this pin.
Figure 3-7 Connections of the RESIN_N pin
As the RESIN_N and POWER_ON_OFF signals are relatively sensitive, it is
recommended that you install a 10 nF–0.1 µF capacitor near the RESIN_N and
POWER_ON_OFF pins of the interface for filtering. In addition, when you design a
circuit on the PCB of the interface board, it is recommended that the circuit length not
exceed 20 mm and that the circuit be kept at a distance of 2.54 mm (100 mil) at least
from the PCB edge. Furthermore, you need to wrap the area adjacent to the signal
wire with a ground wire. Otherwise, the module may be reset due to interference.
The ME909u-521 module supports hardware reset function. If the software of the
ME909u-521 module stops responding, you can reset the hardware through the
RESIN_N signal as shown in Figure 3-8 .When a low-level pulse is supplied through
the RESIN_N pin, the hardware will be reset. After the hardware is reset, the software
starts powering on the module and reports relevant information according to the actual
settings. For example, the AT command automatically reports ^SYSSTART.
Figure 3-8 Reset pulse timing
The RESIN_N pin must not be pulled down for more than 1s. Otherwise, the ME909u-521
module will be powered off.
Issue 05 (2017-12-15)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
Description of the Application Interfaces
30