Power in OFF mode

[mosgaard2000]

Hi,

I have a nRF52840 board where I have attached a power profiler kit and measures the current consumption in OFF mode.

The power consumption changes when I try different things.

I have this line of code: sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE);

1) If I set the Nordic to VDD=1.8V (VOUT) then the current is dependent on the battery voltage.

Vbat=3.0V I=30uA

Vbat=3.5V I=44uA

Vbat=4.0V I=63uA

Vbat=4.2V I=74uA

2) If I set VDD=3.3V (VOUT) I measures this:

Vbat=3.4V I=80uA

Vbat=3.6V I=32uA

Vbat=4.0V I=33uA

Vbat=4.2V I=34uA

3) VDD=2.7V

Vbat=2.85V I=80uA

Vbat=3.0V I=29uA

Vbat=3.3V I=30uA

Vbat=3.8V I=32uA

Vbat=4.0V I=35uA

Vbat=4.2V I=41uA

Is the chip using different regulators to create VOUT in OFF mode?

If VDD=3.3V I guess I can't go below 3.5V on the supply and that is why the current increases below 3.5V - is this correct?

Do you hae any guess why the VDD=1.8V changes so much in current compared to VDD=2.7V or VDD=3.3V?

Regards,

Morten

[Stian Røed Hafskjold]

Hi, you can't use the PPK to measure current when the nRF52840 is in high voltage mode. The PPK supplies voltage to the VDD_nRF domain on the DK, which is the same domain as the REG0 output. The PPK was released before the nRF52840, so it is not compatible with the new REG0 (high voltage) stage on the nRF52840.

The output voltage of the PPK has to match the DK voltage (VDD_nRF) when stacked on top of the DK, so set the regulator switch in the DK position so it uses the same voltage source. If you have a custom board you can connect the PPK directly to VDD on the custom board using the DUT output header, and supply whatever voltage you want on the external supply pin on the PPK (up to 3.6V). Then the PPK will power the board and measure current at the same time.

Where is Vbat connected in your setup?

In general, the current consumption in system OFF mode is less than 1 µA, regardless of voltage level or regulator mode (high/normal voltage). If you measure more than 1 µA in system OFF mode it indicates that there's something wrong with the measurement setup.

[rwilliams]

Hello,

I realize this is an old thread. However, as I am now digging into a nrf52480 project, I too am confused about how System OFF works.

I am using a PCA10056 nrf52840-DK, rev 2.0.1. I am using SDK v2.6.1.
The PCA10056 is programmed with the "peripheral_power_profiling" example. 
The PCA10056 is being powered and measured by a Power Profiler Kit II on the External Supply pins.  
The PCA10056 SW6 is set to "nrf ONLY" and  SW10 is set to "OFF".

The lowest current reading is about ~12uA. According to the above statement, it should be ~1uA.
So, what is wrong with my measurement setup?

Thank you,

Roger Williams
 

[Stian Røed Hafskjold]

Hi, by default the external supply header powers the entire DK including the debugger, etc. You need to set the VEXT->nRF (SW10) switch to ON (and leave the USB cable plugged in to power the rest of the DK). Now the external supply header powers the nRF52 only, and the USB powers the debugger. The reason why you need the USB plugged in is that otherwise the nRF52 will back power the debugger chip through the SWD and nRESET pins (which have internal pullups).