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BQ51050B: BQ51050BRHLR

Jose CM
Prodigy 40 points
Part Number: BQ51050B

Hi!

I wanted information on the calculation of the Rilim and Rterm values for BQ51050BRHLR.

On page 20 of the datasheet the forms are indicated, and this is in relation to the capacity of the battery.

If I have a 180mAh battery, it would be calculated as follows:

Ibulk = 180mA = 0,18A

Kilim= 314 (Typical value to use)

Rfod= 200 (Typical value to use)

The result of applying the formulas are:

Rilim=1.74kOhm

R1= 1.54kOhm

For R5 a 2.4kOhm resistor is usually used

Is this calculation correct? Do you have to take into account something else?

Thanks

Best regards

  • +1
    TI__Guru* 75656 points

    Hello

    The calculations are correct.

    The FOD value is set during FOD calibration and that will take into account losses in battery, pcb, metal around coil and others.  For additional margin recommend increasing R-FOD to 220 ohms and adjust R1 as needed.

  • 0 in reply to Bill Johns
    Prodigy 40 points

    Thank you very much Bill.

    I will take into account the recommendation to put Rfod=220 and adjust the values of R1.

    If by mistake, the calculation of R1 were wrong, what would be the consequences?
    I tell you this because I have a case where the resistors are mounted with an Rfod=562 and R1 is sized for a 110mAh battery instead of 180mAh, which is what is actually mounted. With a resistance of 20%I-bulk.

    Thanks

    Best regards

  • +1 in reply to Jose CM
    TI__Guru* 75656 points

    Hi

    The ILIM setting, R1+ RFOD will determine bulk charge current.  It is important to keep this at the desired value for battery health.

    The RFOD value is used for foreigner object detection, it will report received value back to transmitter.  Larger value equals more received power and less likely to trip FOD fault. Typical range is 200 to 250.