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TPS22965: how did TI get 6A maximum current

yongqiang.sun
Prodigy 10 points
Part Number: TPS22965


Hi，

TPS22965 is a 6A load switch. however how did you get this value ?   what temperature did you calculate this 6A value ?  i read the datasheet, the max Tj is 125C, on-resistance is 25mR, if the current is 6A, then the ambient temperature is 59.84C.  so i am wondering how did TI get this 6A current. 

Thank you.

Eric

  • 0
    TI__Mastermind 36305 points

    Eric,

    I'm not quite sure how you are calculating 59.84C, however generally to get a ballpark estimate we use the following equation:

    Since very little voltage is dropped over the FET, the actual voltage on the input doesn't factor in too much., These all depend on the thermals/layout, however the main variable here is on-resistance and how hot the integrated FET gets. To calculate this, you use the following formula:

    Keep in mind that PDIS * Rtheta is going to be the temperature rise- so you have to add that on to the ambient temperature to get the junction temperature.

    That being said- the 6A maximum also has to do with the process limitations of the FET itself and what is has been rated to after long term reliability testing.

    Best Regards,
    Tim

  • 0 in reply to Timothy Logan
    Prodigy 10 points

    Hi Tim,

    Thank you for your explaination.  that means 6A is the limitation of process after long term reliability test, right ?  i am still wondering why this is not 7A or 5A

  • 0 in reply to yongqiang.sun
    TI__Mastermind 36305 points

    Eric,

    We are not able to share our exact internal testing procedures, however 6A is the current level that was come to after factoring in all of the requirements needed to guarantee reliable operation over the lifetime of the device and over the temperature range of the device. 

    Best Regards,
    Tim