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TPS2051B: Is it safe to connect TPS2051B OC (open-drain) directly to EN pin?

Toshiyuki Aoki
Prodigy 10 points
Part Number: TPS2051B


Tool/software:

I’ve created a USB 2.0 circuit as shown in the diagram, using the TPS2051B for overcurrent protection.

In many reference designs, the *OC (Overcurrent) signal is connected to another device, which then drives the EN (Enable) pin. However, in my design, I’ve directly connected the open-drain *OC signal to the EN pin.

Is there any issue or drawback with this approach?

  • 0
    TI__Mastermind 33551 points

    Hi Toshiyuki,

    The way you have the circuit configured is not necessary. 

    When the TPS2051B detects an over current condition, it will shut of the switch without intervention.  The /OC pin is typically connected to a HUB pin that allows the HUB to report the over current condition to the PC with the standard usb driver.

    If the switch is used in system with a MCU, the the /OC pin can be connected to a GPIO on the MCU to allow for the system controller to be informed of the over current condition.

    If you do not need over current reporting in your system, then just float the /OC pin.

    Regards,

    Chuck

  • 0 in reply to Chuck Branch
    Prodigy 10 points

    Hi Chuck,

    Thank you for your reply. I now understand that my current configuration—connecting the *OC pin to EN—is unnecessary.

    When an overcurrent condition is detected and the switch shuts off automatically, is it okay for the EN pin to remain high?
    I’m a bit concerned about whether it's safe to keep EN tied to +5V in that situation.

  • 0 in reply to Toshiyuki Aoki
    TI__Mastermind 33551 points

    Hi Toshiyuki,

    The EN pin can remain high in the over current state, the switch will be disabled and will turn itself back on once the over current condition has been resolved.

    If the device stays in a condition where the load is high enough to trigger over current, then the device will turn on and off repeatedly.  This is done to have automatic recovery in the system.  The turn on/turn off time are short enough that the TPS2051B will be both electrically and thermal safe in this condition.

    Regards,

    Chuck