Current Consumption - NRF9160

[Will Lizardo]

Hi,

I have a customer interested in using the NRF9160 with a 1000mA/h battery.

They want to keep the board sleeping for 15 minutes, wake up and send GPS data position through a CAT-M1 network. My customer wants to keep the device working up to 6 months.

Is it possible? Do you have a spreadsheet that I can use the analyse the MCU parameters?

[Sigurd]

Hi,

Will Lizardo said:

Is it possible?

Yes, this is possible. Let’s say that the customer need 200 days, that is 4800 hours. With a 1000mAh battery, that is 1000 mAh / 4800h = 208 uA avg current. Several of the scenarios listed here is then possible today. Note that we are now on the nRF9160 Engineering A version, so these current consumption numbers will actually be even lower with the production version in April.

Will Lizardo said:

Do you have a spreadsheet that I can use the analyse the MCU parameters?

There is currently no spreadsheet available.

[phipi]

I know this is old, but I'm looking at something similar and this seems like a bit of a stretch to me. From what I've seen GPS can take anywhere from a minute (warm start) to 15 minutes (cold start) to acquire location and consumes about 50mA in the process. Assuming an average 5 minute acquisition time that's 4.2mAh per acquisition. With a 1000mAh battery that would be just 250 connections.

What am I missing?

[Will Lizardo]

Hi Phipi, Nordic will release a new firmware that will improve the GPS performance and acquisition time.

I understood from my sales manager that this firmware would be available in two weeks time.

[phipi]

Thanks for the reply Will. Does this mean that it isn't possible with current firmware, and that the above response is in fact incorrect?

What kind of current were you able to get down to for GPS acquisition?

[Will Lizardo]

Hi Phipi, I do not work for Nordic, so I can't speak on their behalf but currently, the GPS fix is taking 30s+.

I understood that the next fw would cover A-GPS and the same improvements, and the main expectation is to have a fix in less than 10s with a good antenna.

[Sigurd]

If you are testing this on a nRF9160-DK v0.8.5, then note that the v0.8.5 GPS front-end is not good enough to serve as a reference design. We have done a lot of improvements on the GPS front-end in the v0.10.2 DK reference design, that will give better performance.

[phipi]

Sigurd, can you give an estimate of what kind of current consumption over what amount of time we should be expecting to acquire a GPS fix from cold start on the 0.10.2 DK?

[Sigurd]

Hi,

Unfortunately, I don't have any estimate on how long time a cold-start GPS fix takes with 0.10.2 DK, but it should be better than the v0.8.5. It’s also difficult to give an objective answer that you can re-create, since there are several external factors that can affect the time it takes. E.g. if there are buildings, bridges, trees in the area, and the GPS coverage and the weather conditions you have in your area at a given time. As mentioned by Will, we will in the future release A-GPS, that should give time-to-first fix below 10 seconds.

The GPS will consume around ~40mA when searching for the fix, and once you get a GPS fix, you will typically turn off the GPS, and just start it in intervals, and then it will just take a few seconds(between 1 to 2 seconds) to get a fix again(hot-start).