Wi-Fi&Bluetooth Module Series
FC905A_Hardware_Design 21 / 51
Table 5: Definition of Power Supply and GND Pins
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 a
nd 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:
VBAT
VI O
90% VH
2 Sleep Cycles
WLAN_EN
BT_EN
Sleep Clock
Figure 2: Power-up Timing
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.
Description
Min.
Typ.
Max.
Unit
VBAT
9
Power supply for the
module
3.0
3.6
4.8
V
VIO
22
Power supply for module
’s
I/O pins
1.71
1.8/3.3
3.63
V
GND
1, 3, 20, 31, 33, 36
Ground
Pin Name
Pin No.
Description
Min.
Typ.
Max.
VIN_LDO_OUT
21
Internal buck output for the module
-
-
-
