Q:

Non - Ideal Diode and FET mode on power management ICs

Hello reading the datasheet of TPS25942 section 9.4.2, this ic lets you choose the diode mode, either act as a FET or act as a non-ideal diode.  I do not know which mode to choose.  what are the advantages of each mode?  The datasheet only mentions that using the non-ideal diode mode disables the circuit breaker functionality of specific variation of the chip.  
Both cases seems to be able to provide power, and reverse voltage protection is still present on both modes.  What are the use cases where the other one is better than the other? 

A:

In general, ideal diodes are favored because their voltage drop is close to zero, and therefore the dissipation / loss of power is very low.   
But there are examples you require the forward voltage drop.  
From the datasheet:

This mode is activated through DMODE terminal.  This is an active high terminal with internal pull-down.  The terminal is useful in Power-Mux applications to switch over from master to slave supplies and vice-versa smoothly, when two supplies are within a diode drop of each other. 

In other words: when the "diodes" are used as ORing diodes. 
In that case you require the diode forward voltage drop, because that will "reverse bias" the "diodes" connected to the power supplies having a lower voltage. ( in the example below, D2 is "reversed biased"). 

simulate this circuit – Schematic created using CircuitLab
I quoted "diodes" and "reverse biased" because they are not physical diodes, but TPS25942 devices.