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PMP21318: Regarding to the output current

Masakazu Adachi
Intellectual 2500 points
Part Number: PMP21318
Other Parts Discussed in Thread: PMP20878, TPS23881, TPS2373,

Hello team,

I received a question from the customer. I posted this because the customer's requirement specification is similar to this reference design.

Is there anything to be careful about when designing for high current (12A) in the term (10s) as shown below? The typical current is 24V/2.5A in steady state.

Regards,

Masa

  • 0
    TI__Intellectual 2530 points

    Masa,

    It looks like the current is at 12A for 250usec.  To the converter, this is "steady-state" and not a transient.  The converter current limit will have to be set to supply 12A of current.  The inductor will also have to be selected to not saturate with 12A of current.  You will need sufficient output capacitance to provide an acceptable load step response of the output voltage.  You need to evaluate the heating of the FETs for this 10 second period.  Also, how often does this 10 second period occur?  This period will also affect the thermal performance.

    Also, for a 24V output look at PMP20878.

    Thanks,

    David

  • 0 in reply to David Strasser
    TI__Intellectual 2500 points

    Hello David,

    Sorry for the late reply. Thanks for the support.

    David Strasser said:
    It looks like the current is at 12A for 250usec. 

    I was wrong. You are correct. 

    David Strasser said:
    Also, how often does this 10 second period occur?  This period will also affect the thermal performance.

    I will confirm it to the customer.

    Also, Is there a reference design on the PSE side? Customers are particularly interested in the output overcurrent and overvoltage detection features.

    Regards,

    Masa

  • 0 in reply to Masakazu Adachi
    TI__Intellectual 2500 points

    Hello David,

     Is there a reference design on the PSE side? Customers are particularly interested in the output overcurrent and overvoltage detection features.

    Regards,

    Masa

  • 0 in reply to Masakazu Adachi
    TI__Intellectual 2500 points

    Hello David,

    I confirm about following question.  The customer says it will occur in 90 seconds. In other words, 10 sec->90 sec repeats periodically.

    Masakazu Adachi said:
    Also, how often does this 10 second period occur?  This period will also affect the thermal performance.

    Also,  Is there a reference design on the PSE side? Customers are particularly interested in the output overcurrent and overvoltage detection features.

    Regards,

    Masa

  • 0 in reply to Masakazu Adachi
    TI__Mastermind 37031 points

    Hi Masa,

    David is currently out of office. 

    TPS23881 can be used as PSE for Class-8 power. The following 3 parts will be needed for TPS23881 test kits. You can check the mother board and daughter card references designs. Please let me know if you have further questions. 

    BOOST-PSEMTHR-007

    TPS23881EVM-008

    USB2ANY

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    TI__Intellectual 2500 points

    Hello Diang,

    Customers are particularly interested in the output overcurrent and overvoltage detection features. Is EVM considering such protection?

    Also, Is it possible to use the TPS2373 in the following conditions? Or, if there is a device more suitable than TPS2373, could you please introduce it to me?

    Masakazu Adachi said:
    I confirm about following question.  The customer says it will occur in 90 seconds. In other words, 10 sec->90 sec repeats periodically.

    Regards,

    Masa

  • 0 in reply to Masakazu Adachi
    TI__Intellectual 2530 points

    Masa,

    It is difficult to say what the thermals will be with this duty cycle.  The board temperature will have to be measured.  The lowest risk would be to design for 12A steady-state current.

    Thanks,

    David

  • 0 in reply to David Strasser
    TI__Intellectual 2500 points

    Hello David,

    Understood. I would recommend that customers design with a steady-state current of 12A.

    David Strasser said:
    It is difficult to say what the thermals will be with this duty cycle.  The board temperature will have to be measured.  The lowest risk would be to design for 12A steady-state current.

    Also, on the PSE side, do you have a reference design for overcurrent or overvoltage protection, since the PMP21318 had overcurrent detection?

    Regards,

    Masa

  • 0 in reply to David Strasser
    TI__Intellectual 2500 points

    Hello David,

    Understood. I would recommend that customers design with a steady-state current of 12A.

    David Strasser said:
    It is difficult to say what the thermals will be with this duty cycle.  The board temperature will have to be measured.  The lowest risk would be to design for 12A steady-state current.

    Also, On the PSE side, do you have a reference design for overcurrent or overvoltage protection, since the PMP21318 had overcurrent detection?

    Regards,

    Masa

  • +1 in reply to Masakazu Adachi
    TI__Intellectual 2530 points

    Masa,

    The TPS23881 has over current protection.  If you want over voltage protection on the PSE output, I think that would have to be done on the converter sourcing the 56V to the TPS23881.

    Thanks,

    David

  • 0 in reply to David Strasser
    TI__Intellectual 2500 points

    Hello David.

    I understand. Thanks for the support.

    Regards,

    Masa