VDD_RTC pin current consumption

[AlexMelven]

Can you tell me current consumption on pin VDD_RTC, when main power is off, please?
Need for coin cell battery capacity calculation.

[ESP_Faye]

Hi,

VDD_RTC is a reserved pin and powered by internal LDO.
Thus, it can just be NC.

Thanks for your interest in ESP8266 !

[AlexMelven]

So pity!
Is that means, there is no normal way to make RTC clock power backup? If I will make some kind of plug, which need to work by timetable - first powerdown in mains and my clock working wrong? Cloud synchronizing is not enough, because there could be situation when no any internet or internet is down. My device will be small, so I wouldn't want to attach big batteries, hoped to use lithium button battery, if there should be real VDD_RTC power pad, which should eat might be hundreds of nanoamperes I guess. Do you have any solution for RTC power backup?