Hi everyone,
I'm evaluating the nRF54L15 for a very low-power sensor node application powered by a Lithium Thionyl Chloride (Li-SOCl₂) primary cell. The goal is to achieve multi-year battery life, so I would prefer to avoid using an LDO or other voltage regulation circuitry due to their additional quiescent current consumption.
My concern is related to the battery voltage versus the nRF54L15 operating voltage limits.
- nRF54L15 maximum operating voltage: 3.6 V
- Li-SOCl₂ cell open-circuit voltage: approximately 3.67 V
- During TX activity and other load conditions, the battery voltage drops by roughly 0.2 V, bringing it within the MCU operating range.
- During deep sleep, however, current consumption is extremely low and the battery remains close to its open-circuit voltage of 3.67 V.
Because the device will spend most of its lifetime in sleep mode, the MCU could be exposed to approximately 3.67 V for extended periods.
My questions are:
- Has anyone used the nRF54L15 directly from a Li-SOCl₂ cell without regulation?
- Is a continuous supply voltage of ~3.67 V likely to cause any long-term reliability issues, degradation mechanisms, or reduced lifetime even though it is only about 70 mV above the specified maximum operating voltage?
- Could this result in unexpected brownout behavior, leakage increases, flash retention issues, or other side effects over time?
- Are there any Nordic recommendations for powering the nRF54L15 from primary Li-SOCl₂ batteries while maintaining ultra-low sleep current?
- Would a simple diode drop, load switch approach, or another low-Iq solution be preferred over an LDO in this scenario?
Thanks in advance!
