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BQ24072 - Disconnect load once battery falls below LiIon cutoff voltage such as ~2.8V?

lversteinniel
Intellectual 270 points
Other Parts Discussed in Thread: BQ24072T, BQ24072

I am looking at the bq24072T li+ charger for my application. It seems to have all the standard safety features for Li+ except over-discharge protection. I do not see anything in the datasheet the indicates the part will disconnect the load from the battery once the voltage has dropped below Li+ thresholds (usually around 2.8V). Is this not included? What other solutions do you have that would incorporate this? Also, what is the benefit to the Power-Path as opposed to the load being connected directly to the battery as is on the bqTinyII series - they still seem to operate in the same fashion.

  • 0
    TI__Guru 56650 points

    Thank you for posting a question on e2e  forum.

    The bq24072 internal BATFET (Q2) is PFET. Even it is off, the body diode still connects a battery to the load.  There are few ICs can do this protection .

    TI does not market a single-cell stand alone protector.  Please look at industry favorites like the following:

    You can find the data sheets for these protectors at the following links:

    Mitsumi MM3077 – http://www.mitsumi-components.com/Catalog/ic/battery/mm/3077/text01e.pdf

    Seiko S8211/8261 series– http://www.toyomura.com.hk/pdfdata_e/power_e/s8261.pdf

    Ricoh R5426 series – http://www.ricoh.com/LSI/cn/product_power/bmu/r5426x/r5426x-e.pdf

     The recommended implementation schematic is shown in the data sheet and only requires the addition of 1 capacitor, 2 resistors, and the external FETs.  Many implementations use a dual FET package such as the Siliconix Si6968ADQ to reduce the required pcb space and component count.  Some designers choose to place a capacitor (or 2 caps in series) across the FETs to help control the peak spike amplitude when the protector opens due to a short circuit fault.  All of these protectors can be obtained with a variety of trip voltage and delay options to meet your specific design requirements.