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SN74LVC244A-Q1: About θja

tsuyoshi tokumoto
Expert 2630 points
Part Number: SN74LVC244A-Q1
Other Parts Discussed in Thread: SN74LVC244A,

Hello team,

   I have a question about θja of SN74LVC244AQPWRQ1.

   According to the data sheet,that value is described as 83℃/W.

   On the other hand,the θja of SN74LVC244APW is described as
   114.7℃/W on SN74LVC244A data sheet.

 　Those two packages,the electrical characteristics
 　and the switching characteristics look the same.

 　Is the description that θja of SN74LVC244AQPWRQ1 is 83℃/W correct?

Sincerely,
Tsuyoshi Tokumoto

  • 0
    TI__Guru* 97046 points
    Hello Tokumoto-san,
    The θja value given in SN74LVC244A-Q1 datasheet was calculated using an old thermal model of the device.

    The θja value given in the SN74LVC244A datasheet was calculated using our modern thermal model of the device.

    The value given on the datasheet is that guaranteed by TI. If the datasheet for SN74LVC244A-Q1 is updated, then the thermal values will be updated at the same time.

    In practical operation, it doesn't make a difference. Even under extreme stress (100 MHz operation, 100 mA total output current, TA = 125C) the junction temperature won't exceed 140C. Logic devices are typically damaged by exceeding one of the datasheet absolute maximum ratings rather than thermal failure.