N21
Hardware User Guide
Copyright © Neoway Technology Co., Ltd. All rights reserved.
10
Place bypass capacitors close to the power pin of the module to filter out the high-frequency
noise from the power supply.
Ensure that the width of PCB traces for VBAT circuits allows 1A current and ensure no obvious
decrease of loop voltages. Trace width of VBAT should be at least 1mm and the ground plane
should be as complete as possible. The traces of power supply circuit should be as short and
wide as possible.
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. Connect GND pins and bottom
pads to ground to optimize heat sink and separate noise.
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, because the forward
voltage of diode will vary greatly in different temperature and current. The module might not work properly
with a diode power supply.
3.1.2 VDDIO_2P8
N21 provides one VDDIO_2P8 pin that outputs 2.8 V@50 mA.
VDDIO_2P8 is enabled automatically when the module is awake or in running state.
It is recommended that VDDIO_2P8 is used for level shift only and an ESD protector should be added.
3.2 Control Interfaces
Signal
Pin I/O Function
Remarks
RESET_N
12
DI Reset input
Reset at low level
PWRKEY_N 5
DI ON/OFF button
Triggered by low level to start or shut down the
module.
3.2.1 PWRKEY_N
N21 allows startup by the following controls:
Button
MCU
Automatic start once powered up
