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Original question:

BQ25606: USB port detection in embedded device (D+/D- lines)

BQ25606: USB port detection in embedded device (D+/D- lines)

Driscoll Tsai
Expert 1590 points
Part Number: BQ25606

Hi Sir,

 I would like to go more detail about detect timing.

found bad source detect time (tBADSRC, Bad adapter detection duration ) in DS, is this the whole necessary for bq25606?

Also repeat process every 2secs.

"If the device fails the poor source detection, it repeats poor source qualification every 2 seconds."

Should I monitor which pin from bq25606 to understand it will re-try source detection and how to match the timing?

( I assume if we are on corner case such as host has poor power source but D+/D- is functional)

Regards,

Driscoll

  • 0
    TI__Mastermind 25800 points

    Hey Driscoll,

    I am trying to understand your question.

    Are you looking for a way to test the poor source detection on the charger or do you want to understand why it is needed in the charger?

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Expert 1590 points

    Hi Joel,

    I am looking for the charger IC bq25606 behavior when the power source is poor.

    Also how to handle this poor source condition between bq25606 & MCU.

    Regards,

    Driscoll

  • 0 in reply to Driscoll Tsai
    TI__Mastermind 25800 points

    Hey Driscoll,

    The poor source detection will pull 30mA from the input source on VBUS every 2 seconds if when pulling that current, the voltage on the input crashes below a set threshold consistently. 

    In datasheet terms, the charger will sink IBADSRC from VBUS and check whether the voltage on VBUS/VAC is above the VBUSMIN_FALL + VBUSMIN_HYST. A source that cannot handle that current will drop below VBUSMIN_FALL.

    In your MCU, you may choose to monitor the /PG pin to determine whether a valid source has been applied. Do note that /PG also waits until the D+/D- detection has completed as well. As this is a standalone charger, there is a limitation on the information that can be presented to the host besides a hardware interrupt.

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Expert 1590 points

    Hi Joel,

    Actually, i just want to communicate with host through D+/D-, but worried will be interfered by BQ25606 (every 2 seconds detection).

    so should I need add USB switch?

    thanks~

    Regards,

    Driscoll

  • 0 in reply to Driscoll Tsai
    TI__Mastermind 25800 points

    Hey Driscoll,

    I a couple of thoughts on this. 

    First, you should not be able to communicate via D+/D- is there is not a valid port to attach to. A valid port in this case would be standard USB port than can supply the 5V+/- some tolerance and 500m/900m/1.5 A (based on USB port type).

    For poor source detection, the charger will only continue to pulse the USB input source if, when pulling 30mA, the port continues to crash below the bad adapter threshold I mentioned earlier. If the port is valid (i.e. does not drop below 3.8V(typical) when supplying 30mA), the charger will assume this is a valid input source then proceed to perform USB input type detection. This is meant to run only once up to 1s to determine the current capability of the USB port (500mA, 1.5A, etc). This will run only once every time a valid input source is applied.

    In summary, if you do not have a valid USB port, communication will not be feasible. Poor source detection continues every 2 seconds only if the port continues to fail. If it passes the poor source detection, the D+D- detection will happen once to determine the input current limit to set on the charger so as not to overload the input. Once D+D- detection happens, you may communicate with the USB port readily.

    Regards,

    Joel H