N27 Hardware User Guide
Chapter 4 Application Interfaces
Copyright © Neoway Technology Co., Ltd. All rights reserved.
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4 Application Interfaces
N27 provides power supply, control, communications, RF, and other interfaces to meet customers'
requirements in different application scenarios.
This chapter describes how to design each interface and provides reference designs and guidelines.
4.1 Power Interface
Signal
Pin
I/O
Function
Remarks
VBAT
2, 3
PI
Main power input
3.1V~4.3V (typical value: 3.6V)
VDDIO_1P8 47
PO
1.8V power output
Max. 50 mA output, used only for level shifting.
Add TVS diode when using this pin.
GND
1, 4, 10, 22, 32, 46, 58, 60, 67, 70,
72, 73, 74, 75, 76
Ensure that all GND pins are connected to the
ground plane.
4.1.1 VBAT
In GSM/GPRS mode, RF data is transmitted in burst mode that generates voltage drops on the power supply.
Furthermore, this results in a 216Hz TDD noise through the power and the transient peak current is up to 3A.
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 a 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 the diode will vary greatly in
different temperature and current. The module might not work properly with a diode power supply.
The power supply design covers two parts: schematic design and PCB layout.
Schematic Design
Figure 4-1 shows the reference design of the N27 VRTC power supply.
