In our product we are powering the system from the LTC4011 as well as using the LTC4011 to charge the NiMH batteries.
We need a quick way to determine if we are powered from external voltage or the internal NiMH.
I believe that when the /READY line is active (LOW) that would indicate that the system is being powered from external power.
If the /READY line is inactive (HIGH) the system is powered from the internal batteries.
Is this a correct assumption?
The /READY signal is an indication that charge qualification has passed. See the Charge Qualification State section for more info.
In short, no it is not a good signal to tell you whether you are powered by DCIN or the battery. You could consider just using the DCIN voltage to determine this since it will be low when the battery is powering the load.