N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
12
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Ensure that the width of PCB traces for VBAT circuits allows 2 A current and ensure no obvious
decrease of loop voltages. Trace width of VBAT should be at least 2 mm and the ground plane
should be as complete as possible. The traces of power supply circuit should be as short and
wide as possible.
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Noise-sensitive circuits such as audio and RF, should be placed far away from power supply
circuits, especially when the DC-DC is adopted in the design.
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Ensure that the loop is minimum in design with DC-DC since the frequency is high at SW pin.
Place sensitive components far away from SW pin in case of noise coupling. Place feeding
components as close to FB pin and COMP pin as possible.
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Connect GND pins and bottom pads to ground to optimize heat sink and separate noise.
In GSM/GPRS mode, RF data is transmitted in burst mode that generates voltage drops on power
supply. Furthermore, this results in a 216 Hz noise through power and the transient peak current is up to
2A. Ensure low resistance of power supply trace in design to avoid voltage drop.
Never use a diode to make the drop voltage between a higher input and module power. Otherwise,
Neoway will not provide warranty for product issues caused by this. In this situation, the diode will
obviously decrease the module performances, or result in unexpected restarts, due to the forward
voltage of diode will vary greatly in different temperature and current. The module might not work
properly with a diode power supply.
3.1.3
VDDIO_2P8
N11 provides one VDDIO_2P8 pin that outputs 2.8 V@50 mA.
It is recommended that VDDIO_2P8 is used only for level shifting and IO power supply.
3.1.4
On/Off Control and Procedure
Prior to turning on the module, power on the host MCU and finish the UART initialization. Otherwise
conflictions may occur during initialization, due to unstable conditions. ON/OFF is a pin triggered by
low level pulse and used to turn on or off the module.
Power-On Procedure
While the module is off, pull the ON/OFF pin to ground for at least
1.2 second
and then release it,
the module will start.
If the module uses a fixed baudrate, UART port prints an unsolicited message
(
\r\nMODEM:STARTUP\r\n
), indicating that the module is initialized and the UART is ready to respond
to AT commands.
