PlatformInit() causes more current consumption even after device Sleep(System OFF mode)

[Rajendra]

Hi Forum,

 

I am working on nRF52840 THREAD sleepy node and facing an issue in deep sleep mode. The current consumption in deep sleep mode is more-around 60-70 micro Amp.

 

The details are:

Dev kit:    nrf52840 development board

Thread SDK:    nRF5_SDK_for_Thread_v0.10.0_e1c3d11

Thread version:   OPENTHREAD/g6a15261b-dirty

Example used:   mtd_coap_client

 

When the board is put into deep sleep using call NRF_POWER->SYSTEMOFF = 1;  It goes into deep sleep but the current consumption is about 60 – 70 micro Amp.

After exploring the thread_init() function, found that PlatformInit(0, NULL); is causing the issue. I have double checked that PlatformDeinit(); is called before going into deep sleep mode but still some leakage is there.

I also tried following things:

1. Used another example Blinky, added an application timer and after 5 seconds, the same power off call is used but using this code, the device goes into deep sleep mode and its current consumption in deep sleep mode is less than 1 microAmp.

2. I used nrf_pwr_mgmt_init(); and nrf_pwr_mgmt_run() etc, instead of NRF_POWER->SYSTEMOFF = 1, but still the problem persists.

It would be great if you can provide some direction on this.

-Rajendra

[Stian Røed Hafskjold]

Hi, I did some testing, and it seems like going into system off will leave the UART input pins floating.

Try to write this before going to system off, in order to disconnect the input buffer for the UART input pins:

NRF_GPIO->PIN_CNF[7] = 0x2;
NRF_GPIO->PIN_CNF[8] = 0x2;

Pin 7 and 8 are the default CTS and RXD pins on the PCA10056 DK.

[Rajendra]

This worked. As per documentation the  deep sleep current consumption should go below 1uA. Is there anything else missing?

[Stian Røed Hafskjold]

I get it down to 460nA using the same example as you. How are you measuring current? Are you powering over USB? This is known to cause higher current in measurements because of noise. Can you try to use an external 3V supply on the external supply header, and measure current through P22, making sure both SB40 and SB41 is open. Thanks