Comparing Low-Power Microcontrollers

I tested four MCUs for a coin-cell-powered sensor node: STM32L0, nRF52840, SAMD21, and RP2040. Each was woken from deep sleep once per minute to read a temperature sensor and transmit over BLE or LoRa.

Results for sleep current: STM32L052 with RTC = 0.6uA; nRF52840 in System Off = 0.4uA; SAMD21 with standby = 2.1uA; RP2040 dormant = 0.8mA (no RTC). The RP2040 is essentially unusable for coin-cell applications because its sleep current is 1000x higher than the competition.

For BLE transmission, the nRF52840 wins overall because the radio and MCU are on the same chip with co-designed power management. For LoRa, the STM32L0 plus RFM95W gives the best combined power budget due to the MCU's very low active current during packet assembly.