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LM2660: ABS max value , Power dissipation VSSOP (DGK) and Operating junction temperature

Yusuke Mukuno
Expert 7395 points
Part Number: LM2660
Other Parts Discussed in Thread: LM2662

Hi Expert,

Customer is considering about LM2660 absolute max.

Power dissipation VSSOP (DGK) : max 500mW

Operating junction temperature : max 85C 

    > It is described in the Absolute Maximum Ratings section, but is this the operating temperature range?

And, Rja=250C/W (JEDEC board)

Also datasheet describe as below,

(3) The maximum allowable power dissipation is calculated by using PDMax = (TJMax − TA)/RθJA, where TJMax is the maximum junction temperature, TA is the ambient temperature, and RθJA is the junction-to-ambient thermal resistance of the specified package.

In case of TA=25C, Rja=250C/W, Pdmax=500mW, Tjmax will be 150C.   (I know, Rja is depend on each board condition. And, it is depend on Ta max.)

I think, Tjmax value for Absolute Maximum Ratings is 150C, is it correct?

or

Tjmax value for Absolute Maximum Ratings is 85C, and, Rdmax is 500mW. It is calculated with low Ta and  low Rja conditions. ?

Thanks

Muk

  • 0
    TI__Guru 72465 points

    Hi Muk,

    Thank you for reaching out.  Unfortunately the abs Tjmax is 85C.   The 500mW is the limit for -40C ambient.  The datasheet foot note equation already explained it.  Please plug -40C, +85C, and the Rja, you will get 500mW.

    Hope this clarifies.

    Thanks,

    Youhao Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    TI__Expert 7395 points

    Hi  Youhao-san

    Customer is considering LM2662 instead of LM2660. Because the junction temp max is 85C from your comment.

    LM2662 spec is below,

    In case of LM2662, Tjmax=150C. Also, Pd is estimated with Ta=25C.

    In case of  LM2662, What is meaning "the operating junction temperature" in absolute maximum rating?

    Could you please double-check about  the abs Tjmax of LM2660? (85C, is it correct?)

    I'm confusing...

    Thanks

    Muk

  • 0 in reply to Yusuke Mukuno
    TI__Guru 72465 points

    Hi Muk,

    The 150 deg C is the abs junction temperature for storage, namely the IC is not in operation.  The 105 deg C is for operation.  Beyond 105C  TI does not guarantee the functionality.

    Hope this clarifies.

    Thanks,

    Youhhao

  • 0 in reply to Youhao Xi
    TI__Expert 7395 points

    Youhao-san

    Thank you. 

    In case of LM2662 datasheet,

     Note (4) is written in the Tjmax and power dissipation. Also the power dissipation is estimated by Ta=25C.

    The "power dissipation" is meaning power loss, is it meaning during operation. right?  (note(4) is not storage condition)

    I think, 105C is operating temp range, and 150C is Tjmax for absolute max.

    I understand, "Beyond 105C  TI does not guarantee the functionality." I would like to know Tjmax as absolute max that is tolerance for temperature stress.

    Thanks

    Muk

  • 0 in reply to Yusuke Mukuno
    TI__Guru 59715 points

    Hello Yusuke-san,

    Let me check the abs max Tj on LM2660. For LM2660 we recommend to keep the junction temperature below 85C during operation. Everything beyond can degrade the performance. For LM2662 this temperature is 105C.

    The abs max for LM2662 is 150C otherwise most probable the package might get damaged. As the maximum storage temperature for LM2660 is as well 150C, I think this is the same for this device, but will check for you.

    Nevertheless, thermal degrading might start above the recommended operating condition.