The CC3220x 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 8-12 shows the connection.
Section 220.127.116.11.1 lists the external Fref clock requirements.