EK-TM4C1294XL: External Battery for RTC

Hello Nikolaos,

Nikolaos Piliouras said:

Q1 Will the RTC powered by the battery retain the RT data?

Yes, the RTC operational and hibernation memory valid as long as VDD or VBAT is valid.

Nikolaos Piliouras said:

Q2 What is the consumption of the internal circuitry powered from VBAT pin?

Power consumption for Hibernation/RTC under VBAT is found on Page 1883 of the device datasheet, it's at the very bottom of the table for Current Consumption specs that starts on Page 1880 / Section 27.23

Nikolaos Piliouras said:

Q2 After the main power return, is there a need of RTC data synchronization or the transition from battery(3V) to main power (3,3V) will be transparent as desired ?

The Hibernation module power source is supplied by VDD as long as it is within a valid range, even if VBAT>VDD and the transition is transparent so there is no need for synchronization.

Nikolaos Piliouras said:

We are trying to figure out if this can be achieved by removing R39 and provide separate power to TP11 (3,3V-main power or 3V-lithium battery), without enabling hibernation mode.

Are you just using the LaunchPad for evaluation here before making a custom board? Just asking because for your final application you will need to make a custom board. But for testing the viability, that modification sounds like it would work out.