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TPS25810: Current Limiter - IN2 Not Connected for USB 2.0 - No Vconn

Lucas Wassenius
Intellectual 1515 points

Part Number: TPS25810
Other Parts Discussed in Thread: TPS2546

Hi Team,

I have some questions regarding the TPS25810 and current limitation. In order to add stricter current limit requirements on the Vbus line, an power switch might be added to the IN-pins to the TPS25810. The application is DFP using USB 2.0 without need for Vconn switching. 

Questions:

[Q1] Can IN2 pin be left not connected if Vconn support is not required?

  • Without Vconn support, is there a need to power the CC-lines for USB 2.0?
  • Is IN2 sourcing something else internally?

 

[Q2] Is there any other issue with dropping IN1 voltage with external current limiter?

 

[Q3] Is it possible to change the internal current limiter to a lower value(<1.7A)?

Kind regards,

Lucas

  • 0
    TI__Genius 9630 points

    Hi Lucas,

    Based on your questions, do you need a USB Type-C controller? If you are only doing USB 2 and not using the CC pins, you will not need the TPS25810. We offer the TPS2546, a USB A controller which does USB 2.0, and has an adjustable current limit. 

    For the TPS25810, you are not able to change the internal current limit to lower than 1.7A. There are the selectable current limits available in Table 3 of 1.7A or 3.4A. 

    Regards,

    Emma

  • 0 in reply to Emma Hoying
    TI__Intellectual 1515 points

    Hi Emma,

    Thank you for the quick response and idea!
    USB-C is however preferred for my customer due to compatibility and other reasons.

    For my other two questions:

    [Q1] Can IN2 pin be left not connected if Vconn support is not required?

    • Without Vconn support, is there a need to power the CC-lines for USB 2.0?
    • Is IN2 sourcing something else internally?

    [Q2] Is there any other issue with dropping IN1 voltage with external current limiter?

    Does this seem plausible to you or would there be any issues with using a current limiter on IN1 & leaving IN2 not connected?

    Kind regards,
    Lucas

  • 0 in reply to Lucas Wassenius
    TI__Genius 9630 points

    Hi Lucas,

    You must provide IN2 in order to provide power for the CC lines. The device does all communication with the sink over the CC lines so without power for them, no negotiation will take place. 

    How much do you anticipate dropping the voltage?

    Regards,

    Emma

  • 0 in reply to Emma Hoying
    TI__Intellectual 1515 points

    Hi Emma,

    Thank you for the clarification.

    For an USB 2.0 connection to e.g. USB flash memory, would you need the CC handshake?
    Will the connection work without CC handshake? 

    Meaning, if the CC-handshake protocol is not successful(given no power on IN2), will the device still be able to control the power switch?

    In the Primer for USB-C it seems like the only function of the CC handshake at DFP is for Vconn.  However, I understand that it might also be necessary to monitor & Source the CC pins to let the UFP know that it is correctly connected.

    Thank you in advance for you help!

    //Lucas

  • 0 in reply to Lucas Wassenius
    TI__Genius 9630 points

    Hi Lucas,

    You need to provide IN2 for the TPS25810 to work. You cannot have a valid connection USB Type-C connection without Rp on the DPF side of the CC lines and Rd on the UFP side of the CC lines. So if you do not have power on IN2, the TPS25810 will never present Rp, and a valid connection will never occur. CC pins also determines the cable orientation for the TPS25810.  

    Regards,

    Emma