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LMD register in bq2013h

Rocket42
Prodigy 165 points
Other Parts Discussed in Thread: BQ2013H

hello, everyone

i am using bq2013h IC to gauge 2300 mAh Ni-Cd Battery. I encounter the following problem:

in bq2013h, LMD register is 8bits. So this IC only can measure maximum of 256mAh. isn't it?

Also in bq2013h datasheet I see NAC=LMD while NAC register is 16bits. Why so? I don't understand that.

please to explain that to me.

thank you very much!

  • 0
    TI__Guru 73830 points

    The NAC register is larger, because it can count after the the full discharge (LMD) has completed. e.g. counting self discharge. This count will get incorporated into the algorithm as some point. The capacity is stored as a voltage, so you have to multiple the cell capacity by the sense resistor value to store into the LMD register. So, for a 10 mohm sense resistor, the LMD register can support 25600 mAh.

  • 0 in reply to ThomasCosby
    Prodigy 165 points

    thank Sir,

    would I like you see "bq2013HEVM-001 Gas-Gauge IC Evaluation Module".

    in here, sense resistor vaule is 10Mohm ( Mega ohm). If As your above explains, LMD only can support 0.0256 micro Ampere, isn't it?

    because LMD=R.Cap  => Capmax = LMDmax/R=256/10000000=0.0256 micro Ampere.

    on the other, Designed "bq2013HEVM-001 Gas-Gauge IC Evaluation Module" Capability is 3.5 or 4.5 or 5.5 Ah. So how to read Capacity in LMD right in this case?

    pls to explain to me.

    I hope receive your reponse as soon as.

    thank you. good luck!

  • 0 in reply to Rocket42
    TI__Guru 73830 points

    The Mohm in the table in EVM User's Guide means milli-ohm. The text uses a lower case m at other places in the document. It would not make sense to use a mega-ohm sense resistor in any circuit.

  • 0 in reply to ThomasCosby
    Prodigy 165 points

    Oh,,yeah...

    Thank Sir very much

    I understood.... GOOD LUCK everything.

  • 0 in reply to ThomasCosby
    Prodigy 30 points

    Hello, Mr.
    Recently, I also learn BQ2013H chip, experiencing some of the following questions, please give me your answer:
    1 NAC register on the issue, I would like to read the NAC (available capacity registers) by which the value of simple microcontroller to accurately display the power, but the problem is I do not know how to read out the data is converted into electricity that I want data?
    2 About BQ2013H initialization problem, I tried many methods, but without success, it seems there is no talk of a detailed user manual.
    These are my questions, looking to get your answer. Thank you.