The power consumption of the nRF52840 during advertising

[Karthik p]

BLE settings:

1) Advertising interval: 500 ms.

2) I am not explicitly turning on the DC-DC regulator; I am using the default settings.

3) Tx payload: 31 bytes.

According to the online power profile simulator for my settings, the average current should be 30 µA. However, the actual power profile reading is 60 µA.

What can be done to reduce the current?

[Priyanka]

Hi Karthik,

You can have higher power consumption than the online simulator for various reasons:

1. Optimize the data transfer - You can try to adjust your data size and also the data transfer interval to reduce your average current.

2. Disable unused UARTs.

3. Optimize the network configurations.

4. Disable the debugging and logging.

Regards,

Priyanka

[Karthik p]

Hi Priyanka,

Disabled all UART's 

Disabled the debug and logs  

1. The first picture shows the power profile of 1.8V in advertising mode.
2. The second picture shows the power profile of 2.6V in advertising mode.

My questions are:
1. Why is the current consumption so low for 1.8V?
2. Why does the baseline shift when changing the voltage from 1.8V to 2.6V?

BR,

Karthik

[Priyanka]

Hi Karthik,

Do you have any peripherals or extra connections on the DK? Any hardware changes that you have made?

Which sample are you running?

-Priyanka

[Karthik p]

Hi Priyanka,

No changes were made to the code before or after changing the voltage. Only one sensor, which uses SPI and is supplied by an external 1.8V source, is connected to the DK.

BR, 

Karthik  

[Priyanka]

Hi Karthik,

Karthik p said:

Only one sensor, which uses SPI and is supplied by an external 1.8V source, is connected to the DK.

This could be a reason perhaps. Your sensor must have the same voltage level as the nRF device and hence when you increase your supply voltage from 1.8V to around 3V, you begin to back power the external sensor through the GPIOs. 

It would be good to get a detailed description of how you have connected your DK for the current measurements and also the external sensor too.

-Priyanka

[Karthik p]

Hi Priyanka,

/cfs-file/__key/communityserver-discussions-components-files/4/NRF52840-BLE-Power-Profile-.docx

Please go through this Doc.

Note: sensor getting its 1.8v from the external power supply not from the nrf-dk.

BR,

Karthik

[Priyanka]

Hi Karthik,

Karthik p said:

sensor getting its 1.8v from the external power supply not from the nrf-dk.

Yes, that is the problem. The sensor cannot be powered by 1.8V externally if the nRF voltage is higher than 1.8V. So you need to have VDD voltage for both the devices at the same level. 

Also, please put your nRF switch to the "nRF Only" position without which there will be a current flow from nRF VDD to the onboard debugger.

-Priyanka