Question
STM32N6 — Can VBAT be connected directly to VDD at 1.8 V?
Hello ST Team,
I am designing a board using the STM32N657L0H3Q and would like to confirm whether its VBAT pin can operate at 1.8 V when directly connected to VDD.
The proposed configuration is:
- VDD = 1.8 V.
- VDDA18AON = 1.8 V, supplied from the same always-on rail.
- VBAT connected directly to VDD through a 0 Ω resistor.
- No separate backup battery connected to the STM32.
- An external RTC with a CR2032 battery maintains the time when the main power is removed. Retention of the STM32’s internal backup domain is not required after power removal.
In DS14791 Rev 11, Table 25, page 141, the VBAT operating range is specified as 3.0–3.6 V. However, footnote 2 on page 142 states:
“When VDD is connected to VBAT, VBAT_min = VDD_min.”
Could you please clarify:
- Is VBAT = VDD = 1.8 V a supported configuration for normal operation and Sleep/Stop/Standby modes?
- Does this footnote mean that the 3.0 V minimum applies only when VBAT is supplied independently?
- Are there any additional power-sequencing or configuration requirements?
- Is there an official ST reference schematic showing this connection?
Thank you for your clarification.
Best regards,