I am currently involved with a project using the nrf52840. Page 96 of the Product Specification document (4413_417 v1.1) shows the electrical specifications for the HFXO. However, missing from that electrical specification section is the amplitude voltage required from an external crystal. What is the required voltage to be seen at pins XC1 and XC2 of the HFXO? Or is there another document that would provide more detailed information about voltage levels for the XC1 and XC2 pins? Thank you!