Using the Hibernate mode of the nPM1300 chip built into the XIAO_nRF54LM20A results in a sleep current of 0.5 μA or less, which is far lower than that of other boards based on the nRF54L15 and nRF52840. To see what difference this makes in a real-world application, I tested it using a simple weather monitor built with a BME280 and a Waveshare 1.54-inch EPD.
This application alternates between a “Working” period—during which the device wakes up, takes measurements, and displays the results—and a “Sleep” period, repeating this cycle at a fixed interval.
While the total charge consumed during the Working period is nearly identical across all three boards at approximately 12 mC (3.5 seconds), the average current during the Sleep period varies significantly: 0.5 μA, 3 μA, and 8 μA for the nRF54LM20A, nRF54L15, and nRF52840, respectively.
The graph below compares the total charge consumed over operating cycles ranging from 10 seconds to 1 hour.
The LM20A’s advantage becomes particularly significant when the operating cycle is around 10 minutes or longer. In applications where charge consumption during the active period is high and the sleep period is short, however, the benefit of the nPM1300’s extremely low Hibernate current is relatively limited.
Here is the sketch used in the experiment. For the LM20A and L15 BSPs, I used nRF54L15 Boards 1.0.17, while for the 52840 BSP, I used Seeed nRF52 Boards 1.1.13. For the EPD, I used Waveshare’s epd1in5_V2 library, which supports fast redraws.
nRF5254_WeatherMonitor.zip (138.7 KB)
WM_Video.zip (3.9 MB)
In the next installment, I plan to investigate the issue of high cold-boot overhead in applications where the charge consumed during the “Working” period is relatively small.