I’m new to the XIAO nrf52840 but not low power design. I am using a XIAO nrf52850 plain (non-sense) board as a BLE beacon. I’m powering it using a 5V supply to the board (not via USB). I am measuring current from the supply using a uCurrent Gold.
With the board powered from the 5V supply, its uses a minimum of 3ma of current. This is odd since I would have assumed the LDO on the board would be super efficient. If I put the SOC into power-down mode deep sleep, it still draws 1ma from the 5V supply.
If I instead bypass the on-board LDO and supply 3.3V to the board, it draws only 4 uA when idle and about 25 uA from the 3.3V supply when it sends out the beacon. This is what I would expect from the board.
The schematic shows U6 as the 3.3V LDO without any part information. I find it hard to believe that this part would consume so much power.
For now, I’m powering it with a 3.3V source.