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BQ25895: BQ General Selection, Understanding Power Path Limitations

Donald Bosley
Prodigy 180 points
Part Number: BQ25895
Other Parts Discussed in Thread: BQ24160

I'm interested in the features available on the BQ25895, but don't think the power path can handle a certain portion of the application, so I'm looking for suggestions/alternatives.

I have a client who I'm developing a design with that has very low logic power requirements, but has to occasionally drive a small resistive load for 45 seconds to a minute. The draw starts around 18-20 amps and drops down in a reverse log curve, then stabilizes between 6-8A for the bulk of the period. The PWM to control switching across the load is very slow, so I wouldn't consider this a "pulsed" application. The battery is li-poly and is very capable of handling the high draw requirements. What I'm wondering, is if there is a power path in a BQ device that would actually be able to SAFELY handle these current requirements? 

  • 0
    TI__Mastermind 25800 points
    Hey Donald,

    Before I make a couple of suggestions, what features of the bq25895 were you most interested in?

    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Prodigy 180 points
    In order of attraction :
    - Integrated USB Port Type Detection / BC 2.1 (without an extra IC)
    - Price Tag
    - 5A Charge Capability ( we could potentially live with something ~=3A, but not much less)
    - Host interaction with charger during charge cycle for providing useful feedback during charge state to user
    - Available in non-bga package - tolerances req'd for small BGAs, blind/buried vias, and elaborate fanouts aren't cost effective since rest of the layout doesn't require them
    - Power path and ship mode (although power path won't actually work since cap is 9A for one second)

    Thanks.
  • 0 in reply to Donald Bosley
    Prodigy 180 points
    Sorry, BC 1.2...
  • 0 in reply to Donald Bosley
    TI__Mastermind 25800 points
    Hey Donald,

    I think you may want to consider the bq24160/0A/3. These series of parts are BC1.2 compatible and have host control as well, all in a VQFN package.

    If you can live without the BC1.2 integrated detection and limit the input power solely on the input voltage (VINDPM), then I would consider the bq24261M or bq24262.

    All of these parts have a BGATE pin that allow the part to pair and drive external PFETs. This will let you handle the 18-20A pulse load and 6-8A continuous load external. The caveat is that you need to know when your load is going to pulse at such a high current such that you can trigger the device HiZ mode. This will turn on the external PFETs, and allow discharging from your high capacity battery. The other thing is selecting low Rdson PFETs with higher current capability.


    Hope this helps!

    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Prodigy 180 points
    Hi Joel, 24160 was definitley on my radar, so thank you for the suggestion. Can 24160 detect non-standard adapters, like apple, or will it show up as some sort of fault condition, or just as bad, limit the current @100mA?
  • 0 in reply to Donald Bosley
    TI__Mastermind 25800 points

    Hey Donald,

    It won't show up as bad or fault. It will show as an unknown adapter as you stated, and will limit the current to 100mA.

    Regards,

    Joel H