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Original question:

BQ25886: Input current limit

BQ25886: Are the definitions for Divider 1, 3, and 4 from the datasheet defined anywhere?

Charlie D
Intellectual 275 points
Part Number: BQ25886
Other Parts Discussed in Thread: TPS2513

My understanding is that this chip can detect USB SDP, CDP, and DCP adapter types, as well as detect certain non-standard adapters called "Divider 1," Divider 3", and "Divider 4."    However, these dividers are not defined anywhere in the datasheet.  I am guessing that these refer to different resistor divider configurations that can be placed between the D+ and D- pins on the adapter side.  From the related thread I read:

  1. "If you wish to force the D+/D- detection into Divider 3, you must apply 2.0V on D+ and 2.7 V on D-. I suggest you do this by having a resistor divider from a reference voltage to GND. This reference voltage can be created from an LDO tied to SYS or BAT similar to the EVM schematic."

What about Dividers 1 and 4?  Also is there any published documentation from TI that defines these terms as used by the BQ25886 datasheet?  I am asking because it would be good to know what kinds of charger adapters this chip can detect.  I do not plan on forcing the chip into any mode by placing dividers on the BQ25886 side.

  • 0
    TI__Genius 10385 points

    Charlie,

    Let me know if this previous post is helpful to you!

    https://e2e.ti.com/support/power-management/f/196/t/295853

    Thanks,

    Ricardo

  • 0 in reply to Ricardo
    Intellectual 275 points

    Hi Ricardo,

    This does help some. The forum does provide some info on divider 1, 2, and 3. It is sprinkled throughout multiple posts, which is not ideal, although this did lead me to look at the datasheet for the device they are discussing: www.ti.com/.../tps2513.pdf which does provide a good definition for Dividers 1, 2, and 3 in Section 8.3.3 (revised June 2020 version). The descriptions also provides a nice summary of Dividers 1, 2 and 3.

    However, neither that forum post nor the TPS2513 datasheet defines Divider 4, since those devices don't support this configuration (and my internet searches continue to fail me).  Can you provide a definition for that also?  Also, it would be great if the BQ25886 datasheet were to include this information briefly.  Or an application note would be nice (I haven't found one).  I imagine such a note would cover non-standard USB charging adapter configurations used in the industry, which are supported by TI products.

    Thanks,

    Charlie

  • 0 in reply to Charlie D
    TI__Genius 10385 points

    Charlie,

    Divider 4 is 5V at 2.4A for Apple 12W adapters.

    I hope this resolves your issue,

    Ricardo

  • 0 in reply to Ricardo
    Intellectual 275 points

    Ricardo,

    I just realized that the "Divider 1", "Divider 2", and "Divider 3" terms used in the TPS251xx datasheet are not the same as the ones used in the BQ25886."  So, referring to BQ25886, my understanding is now as follows:

    • Divider 1 is Apple 5V at 2.1A (D+ = 2.7V, D- = 2V)
    • Divider 3 is Apple 5V at 1A (D+ = 2V, D- = 2.7V)
    • Divider 4 is Apple 5V at 2.4A (D+= 2.7V, D- = 2.7V)
    • Divider 2 (by process of elimination) must be Apple 5V at 0.5A (D+ = 2V, D- = 2V) which the BQ25886 does not support

    Can you confirm that this is correct?  I am specifically looking to verify that the D+ and D- voltages are correct.

    Regards,

    Charlie

  • 0 in reply to Charlie D
    TI__Genius 10385 points

    Charlie,

    Your understanding of Divider 1, 3, and 4 is correct.

    Thanks,

    Ricardo