CC3120 Datasheet, PDF (23/57 Pages) Texas Instruments – SimpleLink Wi-Fi Wireless Network Processor Internet-of-Things Solution for MCU Applications

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CC3120
SWAS034 – FEBRUARY 2017
Table 4-8 lists the WLAN fast-clock crystal requirements.
Table 4-8. WLAN Fast-Clock Crystal Requirements
CHARACTERISTICS
TEST CONDITIONS
MIN
Frequency
Frequency accuracy
Initial plus temperature plus aging
Crystal ESR
40 MHz
TYP
MAX UNIT
40
MHz
±25 ppm
60 Ω
4.13.4.4 Fast Clock (F_ref) Using an External Oscillator
The CC3120R device can accept an external TCXO/XO for the 40-MHz clock. In this mode of operation,
the clock is connected to WLAN_XTAL_P (pin 23). WLAN_XTAL_N (pin 22) is connected to GND. The
external TCXO/XO can be enabled by TCXO_EN (pin 21) from the device to optimize the power
consumption of the system.
If the TCXO does not have an enable input, an external LDO with an enable function can be used. Using
the LDO improves noise on the TCXO power supply.
Figure 4-12 shows the connection.
CC3120R
TCXO_EN
WLAN_XTAL_P
82 pF
Vcc
XO (40 MHz)
EN
OUT
WLAN_XTAL_N
Copyright © 2017, Texas Instruments Incorporated
Figure 4-12. External TCXO Input
Table 4-9 lists the external F_ref clock requirements.
Table 4-9. External F_ref Clock Requirements (–40°C to +85°C)
CHARACTERISTICS
TEST CONDITIONS
Frequency
Frequency accuracy (Initial plus temperature plus
aging)
Frequency input duty cycle
V_pp
Clock voltage limits
Sine or clipped sine wave, AC
coupled
@ 1 kHz
Phase noise @ 40 MHz
@ 10 kHz
@ 100 kHz
Input impedance
Resistance
Capacitance
MIN
45%
0.7
12
TYP
40.00
50%
MAX UNIT
MHz
±25 ppm
55%
1.2 V_pp
–125
–138.5 dBc/Hz
–143
kΩ
7 pF
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