Regrading Sleep current in nrf52840

[Santhosh_123]

Hi Team,

we have one doubt regarding sleep current when we try to measure with power analyzer(nrf52840 EVM Board) .we got 5.23 micro amps instead of 2.35 micro amps.

we used this example code D:\santhosh\Penny\nrf52840\nrf-NRF52840\nRF5_SDK_17.1.0_ddde560\nRF5_SDK_17.1.0_ddde560\examples\peripheral\ram_retention for current measurement can you help regarding this so it will be so helpful for our team

[Santhosh_123]

Hi kazi,

Thank you for your reply,Yeah for this   \nRF5SDK\17_0_2\d674dde\examples\ble_peripheral\ble_app_pwr_profiling

we are getting 0.3 uA then i think setup is of But

we want to measure the sleep current  for this specification 

ION_RAMON_EVENT System ON, full 256 kB RAM retention, wake on any event 2.35 μA

any example code is there for this?

[Kazi Afroza Sultana]

Hello Santhosh,

You can measure current in two ways, either using source meter mode or ampere meter mode (Nordic Semiconductor Infocenter). The problem with the source meter mode is that you have to make sure that you are not powering the rest of the board ( debugger chip etc) with the Power profiler kit (PPK). The problem with ampere mode is that there is noise on the current measuring header which leads to 5-10 uA current leakage. 

You can find a switch (SW10) on the PCA10056 where you can choose to supply nRF52 directly using the supply header. This switch is called VEXT-> nRF.  So if you now connect the PPK to the external supply header, flip this switch, and leave the USB connected to power the rest of the board, you should be powering the nRF52 from the PPK. You also have to turn the switch (SW6) to nRF Only from DEFAULT to avoid the leakage current. Also remember to reset the board or power on and off after flashing. 

 

Could you please try this first and see what will be the current afterwards? 

BR

Kazi Afroza Sultana

[Kazi Afroza Sultana]

Hello Santhosh,

The example code will be like this - 

void main(void) {

for(;;) {

void main(void){ for(;;){

__WFE();

}

}

When we are talking about RAM retention, we mean that the RAM is retained when the chip is in System OFF mode. But when the system is ON, all RAM is always retained (powered on) unless explicitly power down in code. So basically the above code put the CPU in sleep mode (WFE = Wait For Event). 

Best Regardds,

Kazi Afroza Sultana

[Santhosh_123]

hi Kazi,

Our team went into what you said. But we don't have PPK kit for current measurement then what to do if we want to measure the sleep current?

Same method we followed for the CPU running 

ICPU0 CPU running CoreMark @64 MHz from flash, Clock = HFXO,Regulator = DC/DC   --> 3.3 mA

we got 3.3mA what is in the datasheet without PPK Kit By using this example code

nrf-NRF52840\nRF5_SDK_17.1.0_ddde560\nRF5_SDK_17.1.0_ddde560\examples\peripheral\flashwrite

Now for sleep current we are following this example code 

nrf-NRF52840\nRF5_SDK_17.1.0_ddde560\nRF5_SDK_17.1.0_ddde560\examples\peripheral\ram_retention

IOFF_RAMON_RESET System OFF, full 256 kB RAM retention, wake on reset 1.86 μA 

But we are getting what is given in the datasheet

[Kazi Afroza Sultana]

Hello Santhosh,

Any current measuring device that can accurately measure down in the uA should be ok with measuring current. Unfortunately we do not have official documentation of measuring current by power analyzer. 

However, You can try using source mode of your power analyzer which will power the board on the external header and will measure current simultaneously.  The DK setup will be same as I mentioned before. 

''You can find a switch (SW10) on the PCA10056 where you can choose to supply nRF52 directly using the supply header. This switch is called VEXT-> nRF.  So if you now connect the PPK to the external supply header, flip this switch, and leave the USB connected to power the rest of the board, you should be powering the nRF52 from the PPK. You also have to turn the switch (SW6) to nRF Only from DEFAULT to avoid the leakage current. Also remember to reset the board or power on and off after flashing. 

 ''

Try this and see what would be the outcome. 

Best Regards,

Kazi Afroza Sultana