STM32N6: How to minimize RTC current consumption in VBAT mode?

[Marius007]

Hi,

I am planning to use an STM32N6 in a project where I need a real-time clock (RTC).

My goal is to run the RTC with minimal power consumption. As far as I understand, this involves using the V_BAT domain, where the microcontroller is supplied through the dedicated backup supply pins.

In my application, only the RTC needs to be running, while the rest of the system should be completely inactive. The main supply voltage will be absent most of the time.

According to the datasheet, I end up with a current consumption of about 40.5 µA at 25 °C in this configuration. This seems quite high, especially when targeting a lifetime of around 5 years.

Since it appears that only a small portion of this current is actually used by the RTC itself, I am wondering if there are ways to further optimize the configuration to reach something closer to 1 µA or below.

I would really appreciate any tips, best practices, or measurement results.

Best regards,
Marius

[KDJEM.1 · Accepted solution]

Hello @Marius007 and welcome to the community,

For the STM32N6, the maximum current consumption for VBAT mode is shared in the datasheet:

For minimum current consumption, I recommend you to use an STM32 ultra low power MCUs like as STM32U5.

Thank you.

Kaouthar

[AScha.3]

Hi,

if you want use the N6xx  and need low power RTC , 

i would add a RTC chip, on I2C ,DS3231 is one of the best (temp. compensated TCXO), about 1uA from batt.

>

Highly Accurate RTC Completely Manages All Timekeeping Functions

• Real-Time Clock Counts Seconds, Minutes, Hours, Date of the Month, Month, Day of the Week, and Year, with Leap-Year Compensation Valid Up to 2100

• Accuracy ±2ppm from 0°C to +40°C