IOFF_RAMOFF_GPIO System OFF, No RAM retention, Wake on GPIO 1.2 μA

[Marco Pennacchietti]

Hi,

I am trying to put the micro nRF52 in sleep in the configuration "System OFF, No RAM retention, Wake on GPIO " in order to spend 1.2 uA.

After start:

configure all IO in INPUT,

enable WDT,

anable the timer and,

anable the interrupt to wake up the micro on PIN PO_19:

    nrf_drv_wdt_config_t config = NRF_DRV_WDT_DEAFULT_CONFIG;
    err_code = nrf_drv_wdt_init(&config, wdt_event_handler);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_wdt_channel_alloc(&m_channel_id);
    APP_ERROR_CHECK(err_code);
    nrf_drv_wdt_enable(); 

    err_code = app_timer_init(); // inizializzazione RTC per funzionamento Bluetooth
    APP_ERROR_CHECK(err_code);
    nrf_delay_us(10000);

   BUTTON_EnableInterrupt();
   gIsButtonSwitched = false;

   gIsButtonSwitched = false;
   while(!gIsButtonSwitched)
   {
        __WFE();
   }

In this situation when the micro fall in the __WFE condiction on my instrument I can found a peack of current comsuction every about 21 mS.

So the average current comsuction is about 3 uA and not 1,2 uA.

What does this peak of current depend on?

Marco

[Håkon Alseth]

Hi,

 

If assuming nRF52832, The average current in this case includes WDT, RTC, and RAM retained, so the base current would be in the order of:

1.2 uA + (40 nA *16) RAM blocks + Irtc + Iwdt + Ilfclk = 1.2 + 0.6 + 0.1 + 0.3 + 0.25 = ~2.45 uA

 

Note that the run currents above are given as typical numbers, and you will see a bit of variation from device-to-device.

 

You can see various sleep currents for nrf52833 for instance, here:

https://infocenter.nordicsemi.com/topic/ps_nrf52833/_tmp/nrf52833/autodita/CURRENT/parameters.i_sleep.html?cp=4_1_0_4_1_0_0

 

In this situation when the micro fall in the __WFE condiction on my instrument I can found a peack of current comsuction every about 21 mS.

 This is the regulator refresh mode. The hardware, in sleep, will duty cycle the power supply based on what the voltage is of the internal regulators. It has a given "low voltage threshold", where it charges up the external capacitor, which is the reason you see a small periodic in-rush.

 

Kind regards,

Håkon

[Marco Pennacchietti]

Thanks

MArco