26MHz TCXO (not crystal) -- which pin to connect to?

[novalight]

Hello @ESP_Angus, sorry for awaking this thread from the death, but I have a question:

since a few years we use a 3V3 HCMOS 2ppm/40MHz Oscillator (ECS-TXO-2520-33-400-AN-TR) , directly coupled to the XTAL_P pin, XTAL_N left floating.

However, just recently I found, that the Hardware Design Guidelines state:

- External oscillator should be coupled via DC blocking cap (why?)
- "The amplitude into XTAL_P can not exceed 1.1 V" (?!)

I want to make sure that our design is stable and does not introduce any WiFi flaws, spurs, bad performance etc.
Can anyone from espressif give background about the requirements above and about our design (said oscillator, direct coupling into XTAL_P)?

Best Regards and thanks in advance!