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TPS22997: SOA limitations for TPS22997

Vitali Lach
Expert 1130 points
Part Number: TPS22997


Tool/software:

Hello,

Using the evaluation board TPS22997EVM as a switch for my current source has destroyed the internal mosfet in TPS22997, the power switch turned into a series resistor of 3.8 Ohm’s. That happened as I changed the Ct (C4) capacitor to 10nF.

My question is: is there any SOA conditions for TPS22997 or power limitations which I have to comply with it? I cannot find anything in the datasheet.

PS: My test setup: current source is based on LT3086 and the load is IR LED SFH4470S. I attached the screenshot for inrush current example where I connected the load by hand:

CH3: output

CH4: inrush current in the load

 

Thank you in advance.

 

Vitali Lach

  • 0
    TI__Mastermind 36781 points

    Hello Vitali,

    Thanks for reaching to E2E.

    There could be abs max violation.

    Refer to 6.1 Absolute Maximum Ratings.

    Is there any way voltage going -ve on output or input?

    Thanks 

    Amrit 

  • 0 in reply to Amrit Jit
    Expert 1130 points

    Hello Amrit,

    thank you for your reply. My design does not exceed the Maximum Ratings, I’ve got 5V input voltage, no negative voltages available. Sinse TPS22997 has a NMOS inside, there could be in general a SOA (Safety Operation Area) limitations. The NMOS could be destroyed in linear mode if it’s operating outside the SOA. This is happened as I changed the Ct to 10nF causing some long timing for linear mode, so I suppose my design was outside SOA. For checking this I need the SOA/Power over time limitations from TI.

    Best Regards

    Vitali

  • 0 in reply to Vitali Lach
    TI__Mastermind 36781 points

    Hello Vitali,

    I understand your concern but for integrated FET devices SOA is taken care already by internal control logic and charge pump mechanism.

    CT=10nF is something which is not tested for this device. you can check datasheet.

    How much turn-on time do you need for this?

    You can check eFuse solutions which has stronger charge pump.

    Thanks 

    Amrit 

  • 0 in reply to Amrit Jit
    Expert 1130 points

    Hello Amrit,

    thank you for that. There is no limitation regarding turn-on time for my design, I changed Ct to 10nF to reduce the inrush current. With 1nF, the inrush current was to high for my overcurrent monitoring. If I understand you correctly, I have to use the recommended values from the application section of datasheet? Maximum capacitive load of 220µF and up to 4700pF for Ct?

    Best Regards.

    V. Lach

  • 0 in reply to Vitali Lach
    TI__Mastermind 36781 points

    Hello Vitali,

    Yes, please use the datasheet recommended values.

    Thanks 

    Amrit 

  • +1 in reply to Amrit Jit
    Expert 1130 points

    OK, thank you very much!

  • +1 in reply to Vitali Lach
    TI__Mastermind 36781 points

    glad it helped

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