Neoway WM620 - Interface Design; Power Supply and Control Interfaces

WM620 Hardware User Guide
Copyright © Neoway Technology Co., Ltd
8
3 Interface Design
3.1 Power Supply and Switch Interfaces
Table 3-1 Power supply and switch interface
Pin
Name
I/O
Function
Remarks
22,
23
VBAT
PWR
Main power supply
3.3 V to 4.2 V (3.9 V is recommended)
26
VDD_1.8V
PWR
1.8 V power supply output
27
VDD_2.6V
PWR
2.6 V power supply output
47
VRTC
PWR
RTC power supply input/output
Not used for any other functions
Ensure that the VBAT never exceeds 4.5 V DC. Voltage higher than 4.5 V DC may damage the WM620
module.
3.1.1 VBAT
VBAT is the main power supply of the module. Its input voltage ranges from 3.3 V to 4.2 V and the
preferable value is 3.9 V. The average current is lower than 500 mA. In addition to digital signals and
analog signals, it supplies power for RF power amplifier.
The performance of the VBAT power supply is a critical path to module's performance and stability. The
peak input current at the VBAT pin can be up to 2 A when the signal is weak and the module works at the
maximum transmitting power. The voltage will encounter a drop in such a situation. The module might
restart if the voltage drops lower than 3.3 V. Thus a large capacitor (e.g. 100 μF tantalum capacitor or 470
μF aluminum capacitor) with low ESR must be installed near the VBAT to avoid or reduce the voltage
drop caused by the RF power amplifier. Figure 3-1 shows the burst current and the voltage drops.