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Current consumption high in system on mode


We are using nRF52840 chip for a power-sensitive application.

We use the UART which is connected to a LoRaWAN module.

Now when I enter the system ON mode after completing sending data via LoRaWAN module, I see that the system on current is about 600mA.

At this point I only have the UART and the RTC peripheral running. There is a fallback timer that has been initialized but is not running.

Does this number look correct? I feel that 600mA in system ON mode is too high even when the UART is active.

I tried disabling the UART and then the current consumption drops to 20uA. But one peripheral consuming so much current doesn't seem correct.

Please advise how we can reduce this current.



  • Enabling the UART doesn't require much current by itself, and for instance transmitting data on TXD will only consume current while transmitting occurs. However when you start rx data, then the chip will draw relative high current, since it needs to have clocks, regulators and easydma channels open to handle the potential incomming data on RXD. So you need to duty cycle the start and stop rx if you want to reduce current consumption, typically this can for instance be controlled by a gpio input, where the peer set a pin high each time it have data to send, and the application can use this pin to start and stop rx.

    Hope that helps,