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BQ2970: Battery Protection Question

BMel
Prodigy 30 points
Part Number: BQ2970
Other Parts Discussed in Thread: CSD16301Q2, BQ2980

I am looking to use a BQ29700 protection IC for a single lithium ion battery. The requirements are a max discharge current of 3.5A, max charge current of 1.25A, UVP of 2.6V and OVP of 4.2V. I believe this will require the BQ29700 to be programmed by TI to have a OCC of 0.071V, OCD of 0.2V. The addition of a MOSFET with RDSon of around 57mOhms should get me close to the requirements. 

Is the above correct? I am assuming I can not model this so how do I go about getting samples? Does TI offer a MOSFET with the above specs?

  • 0
    TI__Expert 7465 points

    Hi,

    We currently do not have a device with that configuration. Please choose an existing device from the device comparison table that will best fit your needs.

  • 0 in reply to Shawn Hinkle
    Prodigy 30 points

    My main use of the BQ29700  is over discharge current protection. I need a max continuous discharge current of 4A instead of 3.5A as mentioned above. I have ordered the BQ29700-EVM-610 but am confused. It states it is rated to 5A and when calculating the discharge current using the CSD16301Q2, I calculate a discharge current of around 2A. I saw this asked in another post on this forum and was never answered. Is the 5A incorrect?

  • 0 in reply to BMel
    TI__Expert 7465 points

    Hi,

    The max operating discharge current is different than the OCD protection threshold. Design example 10.2.1 in the datasheet walks through the calculations and component selection for a set of requirements. Follow this process to determine which FET to use. You can also note in this example, the max discharge current is 7A, but the protection will kick in at 4.5A. 

    Please note that Rds_on does vary across voltage and temperature. This means the current protection accuracy will also vary. If this is not fit for your application, the BQ2980 offers a better accuracy by using a sense resistor for current protection.