Wi-Fi&Bluetooth Module Series
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3.6. Other Interfaces
3.6.1. WLAN_SLP_CLK
The 32.768 kHz sleep clock is used in low power modes, such as IEEE power saving mode and sleep
mode. It serves as a timer to determine when to wake up the FC909A to receive signals in various power
saving schemes, and to maintain basic logic operations when the module is in sleep mode.
Table 17: Pin Definition of WLAN_SLP_CLK
Table 18: Recommended WLAN_SLP_CLK Parameter
3.6.2. XTAL_IN/OUT
The XTAL_IN and XTAL_OUT are external crystal pins, and the recommended crystal frequency is 26
MHz. These pins are optional, and the crystal position has been reserved inside the module. The
following table is the recommended crystal parameters. It is recommended that customers select the
crystal according to the following table and based on their actual needs:
Pin Name
Pin No.
I/O
Description
WLAN_SLP_CLK
24
DI
External 32.768 kHz low power clock input.
Parameter
Value
Unit
Frequency
32.768
kHz
Frequency accuracy
±200
ppm
Duty cycle
30
–
70
%
Input signal amplitude
200
–
3300
mV, p-p
Signal type
Square wave or sine wave
-
Input impedance
> 100
k
Ω
Crystal load capacitance
< 5
pF
Clock jitter
< 10000
ppm
