Quectel FC908A Hardware Design page 22

GND 1, 3, 20, 31, 33, 36
The FC908A 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 tube 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.
When paired with LTE, it is recommended to use 10 pF and 33 pF for C2/C4. The reference circuit of
VBAT input terminal is as shown in the figure below:
VBAT
D1
The time sequence of FC908A power on and off is shown in the below:
Sleep Clock
VBAT
VDDIO
WLAN_EN
BT_EN
It is recommended that VBAT be powered on no later than VDDIO.
FC908A_Hardware_Design
Ground
R1 0R
C1 C2 C3
+
100 μF
1 μF 100 nF
Figure 2: VBAT Circuit
90% VH
2 Sleep Cycles
Figure 3: Power-up Timing
Wi-Fi&Bluetooth Module Series
VBAT
FC908A
C4
NM
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