BLE Power Calculations

[SumitS]

Hi,

I am using the following calculations to calculate the power consumption for the chip:

Formulae to calculate battery power consumption:

Current consumption is calculated /hour: BLE Transmission current = 16mA: active for 20ms/ minute, hence active for 1.2 seconds per hour BLE sleep current = 8uA: subtracting 1.2 seconds active period from 1 hour: in sleep for 3598.8 seconds/ hour

Total current consumption/hour = (Active current consumption X time)/3600 + (Sleep current consumption X time)/3600

Total current consumption = (16000 uA X 1.2 s)/3600 s + (8 uA X 3598.8 s)/3600 s

Total current consumption for an hour = 5.3 uA + 8 uA

Total current consumption an hour = 13.6 uA

Total current consumption for day = 13.6 uA X 24

Total current consumption for day = 326.4 uA

Can you please tell me if this is correct or am i wrong somewhere?

Thanks SumitS

[Stefan Birnir Sverrisson]

Hi SumitS

Your calculations make a lot of sense. I am not sure what TX output power you are assuming for your calculations but if we will choose the default 0dBm output power, the current consumption is 10.5mA, but if you have the DCDC converter enabled, the current consumption should be ~8.0mA, see table 37 in the nRF51822 PS.

But then you have to count for all the other factors that contribute to the total current consumption during the TX event. If we assume that you are advertising, you can look at the advertising power profiles in the S110 Softdevice specification v2.0, table 34.

Usually the sleep current is ~3-4uA

More information on how to calculate/estimate the current consumption is given in the current consumption guide.

As the power profiles show, you need to account for some processing in each advertising event as well, in addition to the TX and sleep current, so 5.3uA + 4uA+ some processing.