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LMK00334-Q1: Does high ambient temperature cause degradation of Long-term stability?

Lijia Zhu
Expert 3640 points
Part Number: LMK00334-Q1

Hi team,

I have a question about the Long-term stability of this chip.

Let's assume the Power Dissipation is 0.5W. There is a heat sink on the case of Chip. The ambient/board temperature is 110 deg and the junction temperature is <125 deg in this case.  However, according to the D/S, ambient temperature should <105 deg. Will this cause degradation of Long-term stability?

As far as I understand, the rqmt of ambient temperature < 105 is at the case that no heat sink on the top. As 115 deg-0.5W*38.1 deg/W≈105 deg. please help to check.

B&R

Lijia

  • 0
    TI__Expert 3640 points

    correction：125 deg (limitation of junction temperature ) - 0.5 W * 38.1 deg/W≈105 deg

  • +1 in reply to Lijia Zhu
    TI__Mastermind 29010 points

    Hi Lijia,

    If you have a heatsink on the top surface of the device to help improve thermal transfer, and you are confident that the device junction temperature is below 125°C, the maximum ambient temperature in the table can be exceeded without creating excessive long-term stresses. Ultimately the junction temperature limit is what matters, as junction temperature is used for HTOL measurements (with Arrhenius equation to model rate of reaction at maximum allowed Tj), electromigration simulations (similar Arrhenius equation-based model), and other long-term reliability assessments.

    As a side note, adding a heatsink on top of the device can sometimes create a capacitive coupling path for high frequency noise, especially if that heatsink is in close contact with other noisy circuits on the PCB such as inductors for switching supplies. Ideally the heatsink metal should be held at a fixed voltage (preferably the same as pad GND) to help prevent noise coupling.

    Regards,

    Derek Payne