In iWave SOM, PMIC chip from Dialog Semiconductor is used for RTC.
VRTC_3V0 pin on G35M ZU19EG SOM, power rail is connected to the PMIC. As mentioned in SOM Hardware User guide the VRTC_3V0 power rail supports from 0V(Min) to 3.15V(Max). And the current drawn is 1.1uA.
For further inquiries, please get in touch with mktg@iwave-global.com
Please find the detailed G35M product information in the below link,