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ESD351: BQ25886 - USB power supply ESD protection

Alessandro Rigoli
Prodigy 210 points
Part Number: ESD351
Other Parts Discussed in Thread: BQ25886, TPD4E001, TPD4E6B06, TPD4E1U06, PMP40496, TVS0500

Good Morning,

I had a problem concerning the part number BQ25886 [ https://e2e.ti.com/support/power-management/f/196/p/935777/3458986#3458986 - BQ25886: voltage on VBUS pin when battery is connected and no power supply is connected to VBUS (OTG charge disabled) ]

One of your colleague solved my problem. It was caused by part number WE 824015 (reference D3): apparently, the protection diode of VCC remained biased even if no USB cable was inserted, and an unwanted voltage on OTG_VBUS appeared. I removed D3 and such unwanted voltage disappeared. 

However, I need ESD protections on USB lines (D+,D-, ID, VCC/GND). Could you please suggest one or more part numbers which are suitable for USB ESD protection and which are compatible with part number BQ25886 thus not causing the same problem? (maybe something that you've already used in one of your designs which you are sure that works correctly) 

Thank you so much, kind regards.

  • 0
    TI__Genius 10652 points

    Hi Allessandro,

    I think the problem might occur because of the follwing. When there is no voltage present on OTG_VBUS, the diodes which are shorted internally to VCC are no longer reverse biased but forward biased which leaves the potential for OTG_VBUS to be charged by forward conduction of the diode array.

    I understand your concern. Normally we might recommend TPD4E001 for this which is P2P with WE824015, but there is still a potential for the same issue.
    To solve this issue, you can also try simply disconnecting Pin 5 frmo OTG_VBUS and to use a seperate ESD solution on OTG_VBUS if yo uwish. Note that this would allow slightly higher signal positive signal swings on your data lines if VCC is disconnect.

    Also, can you take a look if TPD4E6B06 or TPD4E1U06 which is quad-channel ESD protection IC can meet your requirements for the signal lines. If you need a protection for OTG_VBUS we can help with that as well. Since this is not a signal line you can elect to use a different solution.

    Please let me know if this answers your question. And let me know if you have further questions on this topic.


    Best

    Dimitri

  • 0 in reply to dimitri james
    Prodigy 210 points

    Good Morning Dimitri,

    thank you so much for your explanation.

    I know understand the problem. It was due to a pull-up resistor on OTG_ID line which charged OTG_VBUS by forward conduction of the diode array, as you clearly explained.

    In order to avoid such problem, I want to use separate ESD solutions for VBUS and I/O lines.

    I saw your suggested part number TPD4E1U06 and it seems a good choice for I/O lines protection. Concerning VBUS, I saw the schematic PMP40496 for battery-powered system reference design and you used NXP TVS PTVS13VS1UR for VBUS protection. I was thinking of choosing a TVS diode with lower clamping voltage in order to have a higher safety margin wrt BQ25886 maximum absolute ratings on VBUS pin. If you want to suggest a TI TVS diode equivalent part number it would be appreciated.

    Again, thank you so much. Kind regards.

  • 0 in reply to dimitri james
    Prodigy 210 points

    Good Morning Dimitri,

    thank you so much for your explanation!

    I now understand the problem. It was caused by a pull-up resistor to 3.3V on the OTG_ID line which charged OTG_VBUS by forward conduction on the diode array, as you clearly explained.

    In order to avoid such problem, I want to use separate ESD solutions for OTG_VBUS and I/O lines.

    I saw your suggested part number TPD4E1U06, and it seems a good choice for I/O lines protection.

    Concerning OTG_VBUS, I saw your schematic PMP40496 for battery-powered system reference design, and you used NXP TVS PTVS13VS1UR for VBUS protection. I'm thinking of using a TVS diode with lower clamping voltage in order to have a larger safety margin wrt BQ25886 absolute maximum ratings on VBUS pin. If you want to suggest a TI TVS diode equivalent part number, it would be appreciated.

    Again, thank you. Kind regards.

  • 0 in reply to Alessandro Rigoli
    TI__Genius 10652 points

    Alessandro,

    I recommend to take a look at TVS0500 for VBUS protection. This device stronger surge protection spec which is suitable for power rails, and lower clamping voltage as you need.

    Please let me know if anymore questions!


    Best

    Dimitri

  • 0 in reply to dimitri james
    Prodigy 210 points

    TVS0500 should work. 

    Thank you!

  • 0 in reply to Alessandro Rigoli
    TI__Genius 10652 points

    Alessandro,

    Perfect. Please reach out if you have any future questions.

    best

    dimitri