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TPS54227 Current Protection

watanabe
Expert 1740 points
Other Parts Discussed in Thread: TPS54427

Hello,

My customer have a question about OCP of TPS54427.

In the section 7.3.4 Current Protection(Datasheet P8),
It is written with [If the overcurrent condition exists for 7 consecutive switching cycles, the internal
OCL threshold is set to a lower level, reducing the available output current].

My understanding is that [After the over-current limit, current flows.], am I correct with this?

In addition, when the current is flowing,  What is the range of the current?

And,Why current continues to flow?
(Does it flow in what route?)

Best Regards,

-Watanabe

  • 0
    TI__Guru**** 191445 points
    TPS54427 uses valley detect current limit. The current is sensed during the low side FET on time. During this time, the current is decreasing. If the current is near the limit it will be positive, that is flowing out of the SW node, but decreasing. If the current is above the limit at the end of the off time, the low side switch will remain on until the current is below the limit, then a new switching cycle begins. If this occurs for 7 consecutive cycles, on the 8th cycle a new lower current limit is established. Current is still flowing. It is positive and increasing during the high side on time and positive, decreasing during the low side on time. The nominal current limit is 5.3 A. The current will range above an below that by 1/2 ILp-p (which depends on the application Vin, Vout and Lout).
  • 0 in reply to JohnTucker
    Expert 1740 points
    Hi, Tucker
    I appleciate for quick reply.

    When the internal OCL is set to a lower level,
    How much current flows?

    Best regards,
    -watanabe
  • 0 in reply to watanabe
    TI__Guru**** 191445 points
    It is not specified. If memory serves it is reduced to 80% of the nominal value.
  • 0 in reply to JohnTucker
    Expert 1740 points
    Hi,Tucker.

    Thanks to you I was able to understand that.

    Best regards,
    -watanabe