• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 12 subscribers
  • Views 493 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ISOW7841: Continuous Operation at Max Current (~130mA) - Device Temperature

Tom Carpenter
Prodigy 80 points
Part Number: ISOW7841


Hi,

We are using three ISOW784x series isolators to power and isolate control signals from an ADC and amplifiers.

Because of power requirements, we've split the front end into three sections (amplifier, adc, logic), each of which is drawing about 120-130mA at 5V. The three power regions are seperate so each device is acting individually as AFAIK the outputs cannot be paralleled.

I've noticed quite quickly that the isolators are running on the hot side. The one with highest load and fastest switching is sitting around 70-75*C package temperature (about 50*C above ambient).

As far as I can tell from the datasheet this should be within the operating parameters of the device (<<125*C), and indeed the isolators appear to be working correctly, transferring data and producing a stable 5V output supply (albeit with the usual noise expected from a DC-DC). I've therefore come to the conclusion that the temperature rise is to be expected what with >1W dissipation in the package.

So my questions are really, am I right in my conclusions that such a temperature increase is to be expected? and have the devices been characterised for long term continuous running under these temperature conditions?

Thanks,

Tom

  • 0
    TI__Genius 17100 points

    Hi Tom,

    Thank you for posting to E2E! Yes, this temperature increase is normal and within the specified operating range for ISOW7841. This temperature increase can be calculated using power dissipation for ISOW7841 (maximum specified is 1.02W) and Junction to Ambient thermal resistance, Rja = 56.8dC/W.

    Multiplying these yields an approximate +58dC expected temperature increase at the ISOW7841's highest power dissipation. Since your ISOW7841 units are operating below this maximum at ~130mA loads, their power dissipation is slightly less and also within recommended operating conditions.

    The devices are specified to operate at these temperature conditions for their entire lifetime.


    Thank you,
    Manuel Chavez

  • 0 in reply to Manuel Chavez
    Prodigy 80 points

    Thanks for the quick response Manuel.

    It's the first time we've used one of these parts at max load, so haven't previously seen such a temperature rise. Glad to know it's normal.