Q: FAQ: Clocking the 32 kHz oscillator externally

The 32 kHz oscillator is designed with a differential input so to get optimum results one should drive both XOSC32_Q1 and XOSC32_Q2 with one of them being the inverted of the other.

The duty cycle should be within the 30-70% range.
The amplitude of the input signal should ideally be rail-to-rail.
Frequency should be in the 10-40 kHz range