I have a following issue, which I didn't see in IC books: I would like to know if it is possible to send analog signals (sin waves) between two power domains in an integrated circuit. The issue looks as at the picture.

I have never had a problem with sending digital signals between two different power domains as it is done through level shifters / level converters. However, I never thought about sending analog signals between two power domains. Is it done using protection diodes as at the picture?

Of course, signal send from 3.3 V domain is limited to 2.5 V. This sinusoidal 3.3 Vpp emphasizes that signal is send from 3.3 V domain to 2.5 V domain and that maximum signal that can appear on the line is 3.3 Vpp.  

common strategy -

1 convert signal to a differential current (think diff pair)

2 take the differential current and terminate the two currents in a pair of resistors (or active loads) connected to the new power supply rails,

3 receive the new signal into a differential receiver

done

As an example of sending an analog signal between two different power domains see Fig. 32 and Fig. 49 here: [link](http://www.ti.com/lit/ds/symlink/afe031.pdf) . The input signal of the PGA1 is 10Vpp while the PGA2 can support input signal equal to its power domain that is 3.3 V. these two PGAs are connected through low-pass filter LPF and capacitor (C10 in Fig. 49).