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LM25183: OCP test condition

Kevin Huang8
Genius 4636 points
Part Number: LM25183

Hi Team,

How to test the OCP (Over current protection) function?
I saw that ISW = 2.2~2.65A, so the ISW we measure is PIN1 of the IC or Iin of T1?
Is the test method to increase the current at the output terminal of LM25183?
When the ISW reaches 2.2~2.65A, it will be protected or OCP is activated?
When Iout=0.37A, Iin & Isw both have only about 500mA current. (The red box in the circuit diagram below),


It is different from Isw = 2.2~2.65A marked on the datasheet. What is the reason? Or is the test method wrong?

  • 0
    TI__Guru* 78370 points

    Hi Kevin,

    Thank  you for posting. Could you tell what is the waveform in the scope picture?  The peak current can be measured by monitoring the transformer primary winding current, which also flows into the SW pin.  When the peak current hits the limit, it will terminate the on time and hence fulfill the over loading protection. Note that the EC table limits are dc levels, and the detection circuit has propagation delays to activate the protection, hence the observed peak current limit can be slightly higher than those EC table limits.

    Best Regards,

    Youhao