I am developing an application that uses nRF52840 wake on NFC, and spends most of its time in system OFF state with NFC wake enabled.
Per the nRF52840 Product Specification (v1.7, 5.2.1.4), current in NFC sense state is expected to be 100nA. But in my application, I'm measuring about 450nA (with a Joulescope, accurate to ~1nA). I believe I have disabled all hardware blocks that could contribute. The power numbers for other states make sense, so I don't think it's a measurement calibration issue.
I tried the wake_on_nfc example (just downloaded the .hex, didn't recompile) from SDK 17.1, on an nRF52840-DK with external power (2V), USB disconnected, and SW6 set to nRF Only. That also shows ~450nA, so probably my application has turned off everything it can.
I tried my application on an nRF52840-dongle (modified for external 2V power), with about the same 450nA reading. That would seem to rule out any extra parasitic power on the DK, since the dongle is minimal.
So what is the expected power for wake-on-nfc state? Am I misunderstanding the 100nA in the PS? Does anyone see something near that from the wake_on_nfc example?
