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HDC1080: Understanding current consumption values from datasheet

agusta mir
Intellectual 480 points
Part Number: HDC1080

Hi,

Can you help me understand what the datasheet says about current consumption.

The first column entry says the RH measurement, bit 12 of 0x02 register has typical 190 uA and then 

Average @ 1 measurement/second, RH(11 bit) bit 12 of 0x02 register = 0, 710 nA

What is the difference between these two current specifications? It is quite a bit of a difference - uA vs nA. There is a separate entry for startup current too, so I don't know what the difference between the first two are.

  • 0
    TI__Guru* 90886 points

    Dear agusta mir -

    Yes - I am glad to help you understand the way current consumption is considered. In the section you are referring to, there is a note 6 which refers to the conversion time parameter, which is RHCT, further down in same table. If you take the current consumption and spread it out over the conversion time, you will get the average current consumption. It seems there might be a slight rounding offset in the typical current consumption, but its within 5uA I think, so let's do the math here to get you to the understanding you want. 

    If we consider the formula: IAVERAGE = ICONVERSION x TCONVERSION, then apply the 11 bit values to solve...

    IAVERAGE = ~190uA x 3.85mSec

    IAVERAGE = 731.5nA (using typical data sheet values), which is ~21.5nA higher than what we have in DS for typical value. (if we look backwards, the typical DS average value indicates the typical current is about 184.4uA, which is why I think it is a slight rounding error, but close enough i think for this kind of low current measurement. 

    Hope that helps you out.