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

Maximilian Hoferichter
Prodigy 60 points
Part Number: BQ25606
Other Parts Discussed in Thread: TS3USB3000, TS3USB3200

Hi,

I´m currently working on a schematic for an embedded device which should commuicate to the PC via USB and should be powered by a battery pack charged via the BQ25606. So I have to use the same USB port for charging and communcation. Can I simply just wire the D+/D- I/Os of the BQ25606 in parallel with the Data lines of my embedded device or will this cause errors in charger detection or data communication?

Cheers

  • 0
    TI__Mastermind 25800 points
    Hey Max,

    On the bq25606, the D+/D- lines become High Impedance after the detection completes.

    However, you must ensure that your embedded device waits for the detection to complete before attempting to enumerate/communication with your PC. Otherwise, any reflected impedance on the D+/D- pins from embedded device could affect the input detection on the charger.

    Preferably, make the D+/D- pin high impedance while connected to your embedded device.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Prodigy 60 points

    Hi,

    thanks for your reply, Joel.

    I tried to get get my BQ25606 evaluation board running with my BeagleBone Black in parallel on the D+/D- lines. The BQ detects the port correctly (USB2.0) but when I start my BeagleBone after the detection I can´t access it via USB while the D+/D- are connected on the BQ.

    So I think about a little switch do keep the D+/D- lines on the correct device. I think that should be possible with the TS3USB3000 or TS3USB3200 (preferarble because it can be powered direct from VUSB). My embedded device´s D+/D- on the MHL lines and the BQ25606´s D+/D- on the USB lines. When my device powers up it will drive the SEL1 high so the MHL lines to my device will be active and set up for USB enumeration.

    You think this will work or do you have an easier solutions in mind?

    Best regards
    Max

  • 0 in reply to Maximilian Hoferichter
    TI__Mastermind 25800 points

    Hey Max,

    My first suggestion would be to add ~100-150Ohm in line with the D+/D- pins going to the charger to the main bus and see if this improves the situation.

    I.e. Beagle bone D+/D- and PC USB D+/D- are connected, and charger D+/D- pins are connected to this via the 150Ohm resistors. 

    If this does not work, then yes, I would consider the TS3USB family of parts to do the switch. However, be sure the default state of the switch is connected to charger, such that detection can complete. Then switch to your BeagleBone. 

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Prodigy 60 points

    Hi Joel,

    thanks for your suggestion. First I tried to use 100Ohm Resistors in the D+/D- lines of the BQ25606 and got a connection but it was unstable. With 150Ohms it works totaly fine. Thanks a lot for your help. You guys are doing a great job here in this support forum.

    Cheers

    Max

  • 0 in reply to Maximilian Hoferichter
    TI__Mastermind 25800 points
    Hey Max,

    Thanks great! Let us know if you have any more questions.


    Regards,
    Joel H