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ST average current consumption formula vs other methods

jg_spitfire
Senior

Hi, I am trying to calculate the current consumption for my BL072z board

1.- my formula:

16mA in run mode

30uA in stop mode

T to tx data = 20 secs

Number of txs in a hour = 3600/20 = 180

duration of each tx = 3 seconds

total TX time = 3(180)=540 seconds = 0.15 hours

time in sleep mode = 0.85 hours

Total current consumption = 0.15(16mA) + 0.85(30uA) = 2.43mA

Battery = 1000mAh

Capacity is automatically derated by 15% to account for some self discharge so:

Battery = 850mAh

battery life = 850mAh/2.43mA = 349.79 hours = 14.57 days

2.- formula from website

is the same result

3.- ST formula

page 9:

IDD = ( T1*IDD sleep / T ) + ( T2*IDD run / T )

T1 = 20 seconds

IDD sleep = 30uA

T2 = 3 seconds

IDD run = 16mA

T = 40 seconds

IDD = 1.215mA

the ST formula gives me a value very different, does anyone knows why?

thanks

1 REPLY 1
JLall
Associate II

Hi,

Because:

T1 = 20s - 3s = 17s

T2 = 3s

T = 20s

This results in 2.43 mA

JC