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TPS2547: Misc. TPS2547 questions

David F. Chan
Expert 5350 points
Part Number: TPS2547

Hi TI,

With respect to the TPS2547,

  • What is the max current the body diode can handle when EN signal is driven low?
  • What is the Vdelta between IN and OUT pin for the body diode to conduct?
  • What happens when OUT pin is powered with 5V and EN pin is floating?

  • 0
    TI__Mastermind 27505 points

    Hi David,

    Find my answers to your questions below

    1. This does not matter as there are actually two FETs internal to the TPS2547 back to back to one another, so one will act as a blocking diode.

    2. There is no minimum Vdelta. As long as EN is pulled high, and there is no other voltage presented on OUT, then the 5V presented on IN will be measured on OUT and current will flow through the device.

    3. Would not recommend doing this. The floating EN pin could float HI or LOW, so the performance of the device in these conditions is not guaranteed.

  • 0 in reply to Adam Mc Gaffin
    TI__Expert 5350 points

    Hi Adam,

    • With respect to item #1, can you please provide data confirming the presence of this back/back FET?
    • With respect to Item #3, a 10kΩ pull-up to 3.3V is currently being used. Would using a 100kΩ pull-up help to avoid the float?

  • 0 in reply to David F. Chan
    TI__Mastermind 27505 points

    Hi David,

    I do not have any data right now, and it may take some time to get this as I am current not sure how to prove the presence of back to back FETs. The only thing I can think of is to analyze the silicon/package itself. The comment about the TPS2547 having a back to back FET architecture comes from the head designer for that part, so check with your customer and see if our word is sufficient enough in regards to proof.

    As far as the pullup, recommend sticking with a 10k ohm resistor as this is what is on our recommend implementation. Having a 100k ohm pullup resistor would help avoid the float, but having that weak of a pullup may effect performance.

  • 0 in reply to Adam Mc Gaffin
    TI__Expert 5350 points

    Hi Adam,

    OK thanks. Do you foresee any issues or concerns bypassing the TPS2547 by simply connecting the D+/D- from the system SoC  to the type-A-connector?

  • 0 in reply to David F. Chan
    TI__Mastermind 27505 points

    Hi David,

    I do not foresee any issues with this, but cannot say with 100% percent certainty as I have not seen any other customer implement it this way as it is not our recommended configuration. For example, some proprietary phones (non-BC1.2 compliant) will not charge in CDP mode unless it detects that there is a host present. So if the DP/DM lines bypass our part, but are still connected to the Type-A port, then technically the host is present and the proprietary phones should be able to charge. However, I do not know if not having those lines go through our part would affect the system. I have a strong feeling that it will not, but once again cannot say with 100% certainty.

    I would advise your customer to not to go this route, and if they do, possibly add in zero ohm resistor options on their development board that connect the DP/DM lines on the TPS2547