I followed SNOA999 for a zero crossing detector using TLV7011 as a comparator. I am not sure about short-circuiting grounds between AC and DC power sources. My concern is creating negative currents on the DC side and thus damaging some more sensitive components.
I tweaked the circuit from the application note to achieve the following:
Where D1 and D2 are schottky diodes.
Vout works as planned in a SPICE simulation. But, my doubt is if by not short-circuiting V- with the inverting input will affect the stability of Vout as zero-crossing reference.