CC3100_15 Datasheet, PDF (17/44 Pages) Texas Instruments – CC3100 SimpleLink Wi-Fi Network Processor, Internet-of-Things Solution for MCU Applications

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CC3100
SWAS031D – JUNE 2013 – REVISED FEBRUARY 2015
4.11.3.1 Slow Clock Using Internal Oscillator
The RTC crystal connected on the device supplies the free-running slow clock. The accuracy of the slow clock
frequency must be 32.768 kHz ±150 ppm. In this mode of operation, the crystal is tied between RTC_XTAL_P
(pin 51) and RTC_XTAL_N (pin 52) with a suitable load capacitance.
Figure 4-9 shows the crystal connections for the slow clock.
51
RTC_XTAL_P
32.768 kHz
10 pF
GND
RTC_XTAL_N ⁵²
10 pF
GND
SWAS031-028
Figure 4-9. RTC Crystal Connections
4.11.3.2 Slow Clock Using an External Clock
When an RTC clock oscillator is present in the system, the CC3100 device can accept this clock directly as an
input. The clock is fed on the RTC_XTAL_P line and the RTC_XTAL_N line is held to VIO. The clock must be a
CMOS-level clock compatible with VIO fed to the device.
Figure 4-10 shows the external RTC clock input connection.
RTC_XTAL_P
RTC_XTAL_N
32.768 kHz
VIO
100 K
Host system
SWAS031-029
Figure 4-10. External RTC Clock Input
4.11.3.3 Fast Clock (F_ref) Using an External Crystal
The CC3100 device also incorporates an internal crystal oscillator to support a crystal-based fast clock. The
XTAL is fed directly between WLAN_XTAL_P (pin 23) and WLAN_XTAL_N (pin 22) with suitable loading
capacitors.
Figure 4-11 shows the crystal connections for the fast clock.
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Specifications
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