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Original question:

TL2575-05: TL2575 Inductor Dimensioning

TL2575-05: Inductor Dimensioning

Eric Kong
Prodigy 50 points
Part Number: TL2575-05
Other Parts Discussed in Thread: TLVM13620

I'm currently using a TL2575 for a application with the following values:

Vin = 24V

Vout = 5V

Peak Iout = 750mA

I have a 100uF input capacitor, 330uF output capacitor and 330uH inductor.

Is the inductor properly sized for the load that I'm drawing?

  • 0
    TI__Guru 68495 points

    Hi Eric,

    Thank you for reaching out.  Could you consider our newer device TLVM13620?  It will have better design tools to help you to get a good start point. 

    I did a quick calculation and your selection looks okay.  However, please also make sure you verify your design by experiment.

    Best Regards,

    Youhao

  • 0 in reply to Youhao Xi
    Prodigy 50 points

    Hello Youhao,

    I verified the design with several experiments. Off the board, I tested it with a 5ohm load and it was able to supply adequate current. However, on the board, the chip's voltage output will drop to 1.3V within minutes of operation. The output will stabilize back to 5V after but the dip is long enough that my other ICs its powering reset.

    Is there something I can add tot he design to fix this? Or do you recommend switching to TLVM13620?

    -Eric

  • 0 in reply to Eric Kong
    TI__Guru 68495 points

    Hi Eric,

    Obviously the load on your board is different from the 5 Ohm resistor.  Could you tell what exactly is connected to output rail on your board, besides the 300uF and the feedback resistors?  

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    Prodigy 50 points

    Hello Youhao,

    I have another 3.3V regulator (TPS62082DSGR) and 140 single channel DAC's.

    Like I said before, everything works properly as it should but not for long.

    -Eric

  • 0 in reply to Eric Kong
    TI__Guru 68495 points

    Hello Eric,

    Could you check if the IC is becoming hot and triggering thermal shutdown?  By the way, which package do you use?

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    Prodigy 50 points

    Hello Youhao,

    I had the same thought. I measured it with a FLIR and the temperature only comes up to 80C. It's 

    I'm using the KTT (TO-263) PACKAGE.

    -Eric

  • 0 in reply to Eric Kong
    TI__Guru 68495 points

    Hi Eric,

    There is also temperature gradient from the junction to the case, and TJ may have reached the thermal shutdown if your heatsink is not adequate. For debugging purpose, could you use a cooling fan to blow the IC and see if the output voltage can be maintained for longer time?

    Thanks,

    Youhao