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TPS25730: Schematic review request

Mike G.
Prodigy 30 points
Part Number: TPS25730
Other Parts Discussed in Thread: TVS2200

Tool/software:

Hi TI,

Can you give me feedback on this simple schematic for TPS25730D sink-only PD?  It is a VBUS-only board with no battery.

In particular, please note in the top right corner that several of the open-drain outputs are being used to sink LED current up to 3.6mA each (depending on what voltage VBUS is at, which may vary from 5-20V).  Is this acceptable or must I instead use a discrete transistor with each LED to reduce current flowing into the open drain outputs?

Also, FAULT_IN is pulled up to LDO_3V3 by a 10k.  This will enable the TPS25730D, right?

Any other feedback is appreciated. 

Thanks,

Not shown: VBUS_IN, CC1 and CC2 are coming from the USB-C connector; also not shown is a TVS2200 clamp on VBUS, as suggested in TPS25730 datasheet.

Mike

  • 0
    TI__Genius 13880 points

    Hi Mike,

    I would not recommend connecting that port directly to VBUS, due to the risk of the GPIO exceeding its max voltage rating.

    For any unused GPIO, I recommend tying to GND, specifically DBG_ACC. I can have a more in-depth review done by end of week. (Though I do not see any readily apparent issues)

    Regards,

    Conner

  • 0 in reply to Conner Gillette
    Prodigy 30 points

    Hi Conner,

    Thanks for the quick reply.  I modified the schematic per your suggestions, specifically:

    • Unused DBG_ACC tied to GND
    • The open drain outputs PLUG_FLIP, CAP_MIS, PLUG_EVENT and SINK_EN_n are all pulled up (100k) to LDO_3V3.
    • The open drain outputs are then used to drive the gates of 4 discrete transistors (3 NMOS and 1 PMOS for SINK_EN_n since it uses inverted logic).

    If you're able to take another look later this week, that would be fantastic.  I mainly want to make sure that FAULT_IN is handled correctly and that the part will turn on.  FAULT_IN is pulled up to LDO3V3 with a 10k resistor.

    Thank you again for your help.

    Mike

  • 0 in reply to Mike G.
    TI__Genius 13880 points

    Thank you for providing the updated schematic, very helpful.

    I've completed the in depth review, and I see no issues with your implementation. If you don't want to use an external LDO, you can use the LDO_3V3 rail for the LEDs, like is implemented in the EVM (shown below):

    Regards,

    Conner

  • +1 in reply to Conner Gillette
    Prodigy 30 points

    Conner, thank you for the review.  Yes, I saw the internal LDO.  It can only source 1mA of current according to the datasheet, but as you demonstrate with your schematic, perhaps that's enough for the LEDs.  I'll look into it.

    Mike