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TPS2543: 5V conflict handling

O'Mellin
Expert 6115 points
Part Number: TPS2543
Other Parts Discussed in Thread: TPS25221,

Tool/software:

Team,

How does device of this generation 25221 / 2543 / 2544 / 2546 handle a 5V coming from a 5 V device ? how does the TPS25xx handle current flowing from its output to its input through the body diode?

Olivier

  • 0
    TI__Expert 6115 points

    team, I found a post on TPS25221 that mentions that the passing element is actually made off of 2 back to back fet, I guess it's the same for the TPS254x ?

    also how does "negotiation" work in case the customer board ( USB power source  protected by TPS254x or TPS25221)  when plugged to a PC ? I guess there will be a 5V conflict at least at the beginning of negotiation ? what happens if the PC 5V is actually slightly higher than the local 5V ? does the TPS25xxx protects against reverse current ( EN is up ) ?

    thanks 

  • 0 in reply to O'Mellin
    TI__Guru 64491 points

    Hello,

    O'Mellin said:
    team, I found a post on TPS25221 that mentions that the passing element is actually made off of 2 back to back fet, I guess it's the same for the TPS254x ?

    I cannot confirm this, these parts are pretty old.  

    The TPS25221 explicitly calls out reverse protection when EN=0V, while the TPS254x only mentions reverse current in the context of EN=0V.  In the ABS max ratings of the TPS2543 the output current is limited internally:

    While the recommended operating condition limits the current to positive values (no reverse current).

    O'Mellin said:
    also how does "negotiation" work in case the customer board ( USB power source  protected by TPS254x or TPS25221)  when plugged to a PC ?

    This will depend upon the capability of the PC.  The only negotiation is expected from the client side device and this is related to the power allotment. https://www.ti.com/lit/ds/symlink/tps2543.pdf#page=14

    If you are looking for negotiation of an explicit contract then consider a type-c or PD device.  https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1381140/tps2543-how-to-connect-tps2543-to-a-usb-type-c-connector/5280054#5280054

    O'Mellin said:
    what happens if the PC 5V is actually slightly higher than the local 5V ? does the TPS25xxx protects against reverse current ( EN is up ) ?

    This appears to be outside of the recommended operating conditions.  I suspect that since both devices are sources there is no load and effectively no power drawn from either source.

    Regards,
    Chris