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TPS74801: TPS74801 OCP waveform and behavior

kevin chang82
Prodigy 220 points
Part Number: TPS74801
Other Parts Discussed in Thread: TEST2

Hi Sir,

Please help explain the OCP waveform for TPS74801.

I increased the I_load slowly by electronic load until OC.

Test Condition1:

Vin:3.3 Vbias:5V Vout:1.8V

Test Condition2:

Vin:3.3 Vbias:5V Vout:1.5V

Test Condition3:

Vin:3.3 Vbias:5V Vout:1V

But Test3 OCP waveform is different with Test1 and Test2

IN test3 ,Iload is drop when OCP happened,but test1 and test2 not.

please help to explain the wavefrom in test3. 

thanks

CH1:Vin CH2:Vout CH3:Iload

Thank you.

  • 0
    TI__Mastermind 23361 points

    Hi Kevin, 

    From the three scope-shots that you shared, 1.8V and 1.5V output options only dropped to 0.5V to 0.6V while the 1.0V option dropped to 0.2V - 0.3V. The difference may be related to different headroom on the Vout and the actual current limit circuit design in this device. Instead of forcing a current using the electronic load, can you try to force a voltage at the Vout and measure the current? When you do the measurement, can you apply forced voltage from 0V to 1V with 0.1V step, this will help to confirm if the difference you saw is due to the headroom. 

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    TI__Mastermind 23361 points

    Hi Kevin,

    We've heard from you for more than one week, and I am assuming the issue has been resolved on your side. If this is not the case, please reply back on this post.

    Regards,
    Jason