RTC Power Calculation

[specneeraj]

Hello NXP,

We are calculating battery life for RTC for which active & sleep current are required for SNVS power domain in RT1176.

However refer to datsheet IMXRT1170BIEC - Table13, page 35, only sleep current is given.

Please let us know the factors affecting the active current and various calculations related to active current for the SNVS power domain.

[Gavin_Jia]

Hi @specneeraj ,

Thanks for your interest in NXP MIMXRT series!

VDD_SNVS_IN supplies power to the SNVS/RTC domain. This domain is an always-on, low-power domain that primarily maintains the 32 kHz RTC, SNVS logic, and related wake-up and safety functions. Its current consumption is only weakly correlated with the active/sleep states of CM7/CM4; therefore, the VDD_SNVS_IN values for the SNVS mode listed in Table 13 are not omitted “sleep-only” data, but rather baseline values that can be used in RTC backup scenarios.

• If the coin cell only provides power when the main power source fails → Use the SNVS mode current estimate directly;
• If the coin cell also supplies power to VDD_SNVS_IN while the system is active, calculate the average current based on the active/SNVS duty cycle.

The main factors affecting the SNVS current include temperature, VDD_SNVS_IN voltage, process variations, leakage from the 32 kHz RTC crystal/board, external leakage from SNVS-related pins, and whether the device has actually entered SNVS mode. Please refer to AN13104 for more details.

Best regards,
Gavin