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TPS54202: Please tell us about OCP operation of TPS54202.

Part Number: TPS54202

Dear sir,

Please refer to the attached file.
And please answer my question.

Best regards,about OCP operation.pdf

H.MUROYA

  • Hi Muroya,

    What is the allowable inrush current value of this IC? Is it up to a current limit of 4A?

    =>Yes, it is up to a current limit of 4A

    Is it OK to consider that if the output voltage of 5V has risen without any problems, then there is no problem with inrush current?

    =>Yes. And the input current is part of inductor current. Need to check whether inductor saturation current is large enough.

  • Dear Vincent Zhang san,

    1; OCP Spec is max4A.
     However, I think this is a numerical value related to OCP operation.
     There should be another spec for the breakdown voltage of the IC internal element against the inrush current. (ASO etc.)
     How is it?
     And what kind of numerical value is that spec?

    2; OCP min spec is 2A.
     If the IC of a certain lot operates in OCP at 2A, what is the rise of this 5V?
     Will 5V not stand up?
     (The rise time of 5V in the document yesterday is 10msec or less. And the inrush current is about 2.7A.)

    Best regards,

    H.MUROYA

  • Hi Muroya,

    For one certain device, the OCP is fixed, slightly changed between temperature. Min 2A or Max 4A is based on milisons samples data.

    1. If the VIN voltgae is below recommend voltage 28V, then device will be safe.

    2. It indicates this device OCP is around 2.7A. If OCP time is very short, 5V could normally built up. If you choose a large COUT at 2A CC load start up condition, after 5ms soft start time, vout is still below 40% of setting voltage, then 5V won't build up. Otherwise it would be fine.

  • Dear Vincent Zhang san,

    1; I am asking the following questions.
      There should be different specifications for the breakdown voltage of IC internal elements. (ASO etc.)
      (IC internal elements.; (Tr, FET, etc.))
      I want to know that Spec. How is it?

    2; In the waveform of my issued this time, why can you say "This device has an OCP of about 2.7A?"
      (OCP; Over Current Protection)
      (2.7A; I report it as an inrush current.)
      Please tell me the reason why you can judge as OCP.

     On the other hand, I understand if your comment is below;
     [It indicates this device ”Inrush” is around 2.7A. If ”Inrush” time is very short, 5V could normally built up.]
     But I want to know more.
     "Inrush" time is very short; how long is it?

     Best regards,
     H.MUROYA

  • Hi Muroya,

    1. I'm still trying to understand your question. 'I want to know that Spec' What Spec you would like to know? . 

    If you mean breakdown voltage relative to different Tr/FET size, We don't have this data. We could only gurantee the minimum breakvoltage is 28V for all TPS54202 devices. Of course breakdown voltage will be impacted by internal parameters, some devices breakdown voltage will be higher.

    2.I 'judge' it's OCP because sometimes device will trigger OCP during startup prcoess at heavy load condition. It would be more clear if you can capture inductor current waveform.

    For short I mean within soft start time.

  • Dear Vincent Zhang san,

    I'm sorry for troubling you.

    1; OCP works at 4A. (Of course it may differ depending on the temperature environment.)
     Normally, I think that the current value of OCP and the maximum rating of internal elements are different.
     How is it?

     You say there is no problem if the input voltage is 28V or less.
     However, even if the input voltage is about 10V, the inrush current (pulse current) will differ depending on the capacitive load on the IC_Vout side.
     In this document, inrush is about 2.7A, but I'm concerned about changes in capacitive load and inrush current.

    2; Your request; I measured the inductor current.
     Please see attached document.

    Best regards,
    H.MUROYAabout OCP operation_addinfo_a.pdf

  • Hi Muroya,

    Gald to answer any questions.

    I'm alos curious what's the load difference between Fig A and First waveform(when you measured PIN3 current)? 

    From my understand,  'Inrush current' into VIN pin is part of inductor current when HS FET is on.Inductor current will be clamped by Hide side current limit and low side current limit. So even there is large output capacitor, 'inrush currnet' wouldn't be higher than 4A, so that's why I say it woildn't break the part.

    From you inductor waveform, FigA and FigB doesn't trigger OCP and in Fig C it triggers OCP becasue of 2A load. Back to you first waveform in Pin3, Inrush current is 2.7A which indicates it haven't trigger OCP(Apologies mis judged).But anyway the inrush current should be lower than 4A.

  • Dear Vincent Zhang san,

    1;Your question;
     ”I'm alos curious what's the load difference between Fig A and First waveform(when you measured PIN3 current)?”
     ⇒There is no difference in load. Both are "(normal startup of this product)".
      The electric(al) current observation point is different.

    2; My understanding from your comments.
     ⇒Inrush current to the VIN pin on the input side does not exceed 4A.
      If it exceeds the limit, the OCP will work.
      Therefore, if the input voltage is 28V or less, the IC will not break.
      Is this all right?
      ⇒Please let me confirm a little more.
       How long does OCP operate?(xx μsec?)

    Best regards,

    H.MUROYA

  • Hi Muroya,

    For your second question,

    Inrush current to the VIN pin on the input side does not exceed 4A. If it exceeds the limit, the OCP will work. Therefore, if the input voltage is 28V or less, the IC will not break.

    [Vincent] => Yes.

    How long does OCP operate?(xx μsec?)

    [Vincent]=> It depends on load and output capacitance condition. ~ msec is also possible.

  • Dear Vincent Zhang san,

    I understand your comment.
    Thanks for your support.

    Best regards,

    H.MUROYA