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TPS25947: Interfacing the TPS25947 with CC controller TUSB319

Nir Alon
Intellectual 640 points
Part Number: TPS25947
Other Parts Discussed in Thread: TPS25946, TPS25948

Tool/software:

Hello all,

In my design, I intend to interface the TUSB319 CC controller with the TPS25947.

The TUSB319 has an ID pin, which is an open-drain output that acts like an EN_N pin (asserted low when the CC pins detect device attachment).

I’m considering using the TPS25947's OVP pin for this purpose, as described in the datasheet:

Section 9.6 – USB PD Port Protection (page 53):

“The PD controller can also use the OVLO pin as an active-low enable signal to control the power path. Holding the OVLO pin high keeps the device in the OFF state in sink mode and blocks current in both directions.”

Ideally, I would use a pull-up resistor connected to VBUS to pull OVP up to 5V, and then connect the OVP pin directly to the CC controller's ID pin.

However, when looking at the absolute maximum and recommended operating conditions for the OVP pin, I noticed something strange:

The EN/UVLO and OVP pins both have a 6.5V absolute maximum rating, which makes sense. However, the recommended operating maximum for the OVP pin is only 1.5V, while for EN/UVLO it’s a much higher 5V.

Does it make sense that the OVP recommended maximum is only 1.5V?

I also checked the EVM schematic and observed the following:

If VIN max is 23V, then the OVP pin will see:
23V × 158kΩ / (158kΩ + 2MΩ) = ~1.68V,
which is higher than the stated recommended maximum operating voltage.

Is the 1.5V figure correct?

Thanks,
Nir

  • 0
    TI__Mastermind 39295 points

    Hi Nir,

    The recommended max of 1.5V is general recommendation as in most applications when using the resistive divider, you select the values such that the value is near the rising or falling thresholds. 

    the device won't get damaged if the voltage is within abs max rating. 

    One thing I would like to mention is if there are any faults, the OVLO pin won't help in removing them and you will have to perform power cycling or wait for auto-retry (depending on the variant).

    Best regards,
    Arush

  • 0 in reply to Arush Gupta
    Intellectual 640 points

    Hi Arush,

    Just to confirm my understanding — the 1.5 V recommendation is not an electrical upper limit, correct?

    If that's the case, I’m a bit confused as to why this value is listed under the electrical characteristics table. I understand that the divider should typically target the rising/falling thresholds, but the 1.5 V figure being presented that way can be misleading.

    Also, thank you for the point about fault handling. One thing I think is worth emphasizing in the datasheet is that only the "A" variant (with auto-retry) should be used when OVLO is repurposed as an EN_N pin, since the others will latch on fault.

    P.S. I’ve attached a portion of the schematic for your reference — it’s specifically related to the OVLO functionality we discussed.
    If you have a moment to take a quick look and confirm that the implementation aligns with the device’s intended use, I’d really appreciate it.

    ID is an open drain output; asserted low when the CC pins detect device attachment

  • +1 in reply to Nir Alon
    TI__Mastermind 39295 points

    Hi Nir,

    Nir Alon said:
    P.S. I’ve attached a portion of the schematic for your reference — it’s specifically related to the OVLO functionality we discussed.
    If you have a moment to take a quick look and confirm that the implementation aligns with the device’s intended use, I’d really appreciate it.

    The implementation looks fine. Just want to add, this device is unidirectional (current only from IN to OUT). I hope your application also requires uni-directional current flow, else consider TPS25946 or TPS25948.

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    Intellectual 640 points

    Hi Arush,

    Thank you for confirming — I appreciate you reviewing the implementation.

    My application is a 5 V provider only, so a unidirectional switch is perfectly suitable.

    Thanks again for your support.

    Best regards,
    Nir