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Table 5: Definition of Power Supply and GND Pins
Pin Name
Pin No.
VBAT
9
VIO
22
GND
1, 3, 20, 31, 33, 36
The FC905A is powered by VBAT. It is recommended to use a power chip with a maximum output current
of more than 0.5 A. To ensure better power supply performance, it is recommended to parallel 100 μF
decoupling capacitors and 1 μF and 100 nF filter capacitors near the input of the module VBAT.
Meanwhile, it is recommended to add a TVS near the VBAT input terminal to improve the surge voltage
bearing capacity of the module. In principle, the longer the VBAT line, the wider the line.
The time sequence of FC905A power on and off is shown in the below:
3.4.2. Buck Circuit Pins Introduction
The following table describes the pin definition of the internal buck circuit of the module:
Table 6: Definition of Buck Circuit Pins
Pin Name
Pin No.
VIN_LDO_OUT
21
FC905A_Hardware_Design
Description
Power supply for the
module
Power supply for module's
I/O pins
Ground
Figure 2: Power-up Timing
Description
Internal buck output for the module
Wi-Fi&Bluetooth Module Series
Min.
Typ.
Max.
3.0
3.6
4.8
1.71
1.8/3.3
3.63
Min.
Typ.
-
-
Unit
V
V
Max.
-
21 / 51
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