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PCM5101A-Q1: Operating temperature range vs. Operating Junction temperature range (in abs max section)

domenyko
Genius 9655 points
Part Number: PCM5101A-Q1

Dear all,

one of my AA has noticed something strange in the Operating temperature range  vs. Operating Junction temperature range (in the abs max section).

The Q1 device is operative from -40degC to +125degC, but in the datasheet the junction temperature max value is 130degC.

According to the thermal parameters, the device will require a heat sink when it operates at 125degC.

Is there anything wrong ? or the MAx Junction temp in the datasheet is wrong ?

regards,

Domenico

  • 0
    TI__Guru 53633 points
    Hi Domenico,

    Max junction temperature is set by the process node that we used to create the PCM device. Which thermal parameters are you referring to? We specify that the device will will operate within specification from -40°C to 125°C.

    Thanks!
    Paul
  • 0 in reply to Paul_Frost
    TI__Genius 9655 points

    Hi Paul,

    I’m referring to the thermal resistance.

    If I consider the power dissipation on page 10 of the datasheet (187mW @DVDD=1.8V, input signal @-1dBFS) and the tetaC 25degC/W the increase of temperature is about 5degC so it means that if TA=125degC the junction temp is close to 130degC.

    This is the source of my concern regarding the operation at 125degC.

    Regards,

    Domenico

  • 0 in reply to domenyko
    TI__Guru 53633 points
    Hi Domenico,

    I think considering only one of the theremal resistance parameters is an over-simplification of the thermal model. Please look over document SPRA953C.
    www.ti.com/.../spra953c.pdf

    There are many thermal factors that effect this, and most of them are in parallel. I would assume that it would be appropriate to put the RθJA and RθJB in parallel, which still gives about 28°C/W...

    Though the spec is still marginal it is within the limits, so I do not think that the datasheet is wrong.

    I will ask our quality manager to see if we are interpreting this correctly, though I think to be 100% percent sure you would need to look at the whole system performance in your customer's application.

    Thanks!
    Paul
  • 0 in reply to Paul_Frost
    TI__Genius 9655 points
    Hi Paul,
    thanks.

    This topic is very important, the application is a VESS and in most of the case all the electronics is in a box which does not have any heat sink (cost reason) and any fan.
    regards,
    Domenico
  • 0 in reply to domenyko
    TI__Guru 53633 points
    Hi Domenico,

    We are interpreting the thermal model correctly, so it may be necessary for the customer to ensure the application TA does not exceed 125°C, or less for additional margin.

    Thanks,
    Paul