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BQ24392 BC1.2 voltage detection / suspend mode

Jonathan9420
Expert 2056 points
Other Parts Discussed in Thread: BQ24392

1. When it measures the DP/DM lines for BC1.2 detection, are these detected voltage ranges proportional to VBUS or are they absolute voltages? For example, if VBUS is 5.5 V, and DP = DM = 3.3, would it still be detected as a TomTom charger because 3.3/5.5 < 3.1/5?  Or is it not, because 3.3 > 3.1?

2. When the SDP host is asleep (DP high, DM low), what are the digital outputs?  Does it keep the USB switch connected and leave it up to the USB IC to handle shutting down the system load / battery charger? 

"If a PD is attached to a Charging Port, (i.e. CDP, DCP...), then it is allowed to draw [1.5 A] without having to be configured or follow the rules of suspend."

But for a SDP in suspend it's still required to limit current to 2.5 mA

  • 0
    TI__Mastermind 45380 points

    1. When it measures the DP/DM lines for BC1.2 detection, are these detected voltage ranges proportional to VBUS or are they absolute voltages? For example, if VBUS is 5.5 V, and DP = DM = 3.3, would it still be detected as a TomTom charger because 3.3/5.5 < 3.1/5?  Or is it not, because 3.3 > 3.1?

    When the BQ24392 measures the DP/DM for BC 1.2 detection, the detected voltage ranges are not proportional to VBUS.  They are absolute voltages.

    2. When the SDP host is asleep (DP high, DM low), what are the digital outputs?  Does it keep the USB switch connected and leave it up to the USB IC to handle shutting down the system load / battery charger?

    The BQ24392 device runs its detection algorithm every time it sees a low to high transition above the Vbus_valid threshold.  Once the BQ24392 has runs its detection and set the digital outputs it will not change unless another detection sequence is initiated. 

    When the BQ24392 device has detected an SDP the USB path will be connected if the GOOD_BAT input is high.


     

    "If a PD is attached to a Charging Port, (i.e. CDP, DCP...), then it is allowed to draw [1.5 A] without having to be configured or follow the rules of suspend."

    The BQ24392 device is designed to tell the controller through its outputs if a charger is detected or not and if it is allowed to charge at full current.  The amount of current or suspend rules will need to be handled by the system according to the appropriate standards.  The BQ24392 does not have any control of the current on the VBUS line but provides the detection algorithm to detect what has been plugged into the USB port and inform the system controller. 

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    Expert 2056 points
    Ok thanks.

    Ok so the datasheet lists what happens if 2.0 < DP < 3.1 (TomTom), and what happens if DP = 5.0 V (PS/2), but what happens if it's between these voltages, like 3.3 V?
  • 0 in reply to Jonathan9420
    TI__Mastermind 45380 points
    Jonathan,

    The BQ24392 device is designed to detect the standardized terminations on the D+ and D- per scribed by USB BC 1.2 specifictation, apple's spec, etc. These terminations are standardized around the world and the BQ24392 algorithm will detect these voltages as a result of the standard terminations. Do you have an example of a charger or accessory that when the BQ24392 runs its detection that a 3.3-V voltage is created?

    Thank you,
    Adam
  • 0 in reply to Adam Torma
    Expert 2056 points

    Can we discuss it in private?


    (Also, apparently Sony chargers use 3.3 V on each data line.)

  • 0 in reply to Adam Torma
    Expert 2056 points
    Also sent to the documentation feedback form:

    In Table 1. Detection Table, in the "Charging Downstream Port" row, with GOOD_BAT low, it says to limit current draw to 100 mA.

    I don't think this is correct, since you can always draw 1.5 A from a CDP, dead battery or not:

    BC1.2: "If a PD is attached to a Charging Port, (i.e. CDP, ...), then it is allowed to draw IDEV_CHG [1.5 A] without having to be configured or follow the rules of suspend."

    The CHG_DET pin is supposed to indicate that a dedicated charger is connected, in which case you can always "Charge with full current", right?
  • 0 in reply to Jonathan9420
    TI__Mastermind 45380 points
    Jonathan,

    The last column in Table 1 "charge current" is a recommendation on how a system should interpret the status outputs from the BQ24392 device. I'm not sure how we determined that recommendation but you may have caught an error in the datasheet.

    You are correct the CHG_DET pin will indicate that a dedicated charger is connected.

    Thank you,
    Adam