• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 61 subscribers
  • Views 87 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

LM5013-Q1: Can't cope with heavy load in cold environment!

Leif Svensson
Prodigy 20 points
Part Number: LM5013-Q1
Other Parts Discussed in Thread: LM5013

Hi, I use a LM5013-Q1 on a power board with nominal input voltage +28V and nominal output is set to +12.5V / 3.5A.

In reality the output voltage is more like +12.8V but is rather sensitive to changes in input voltage. Our problems were discovered when tested in a climate chamber

in -40 degrees centigrade (which is what it should manage) together with an output load of approx. 2 - 2.5 amps. Then the output voltage dipped, like down spikes all the way down to around +7V !

This causes our CPU board which is fed by the LM5013 to reboot.

After that we tested only the power board alone, connected to a 200W power resistor to set an output current of 2.2A.

Then we sprayed "freeze spray" on the board to locate the problem. when spraying the regulator the output voltage dipped immediately to 7 - 8V. It was very sensitive!

You can see the power board schematics above. Parts to the left of the regulator is mainly to minimize EMC and make the board +100V tolerant.

Anyone else who experienced these problems? Any ideas of what's going on, or what to do to solve our problems??

B.R.

Leif Svensson

  • 0
    Prodigy 20 points

    Update:

    We now replaced the LM5013-Q1 with another one identical from the same batch. Then when sprayed with freezing spray the output almost didn't change at all!

    Could it be just this individual chip that had issues with cold environment and heavy load? It seems promising at least. Now we have put the board and the load (two power resistors resulting in approx 2.5A load) in our climate chamber and set it to -45 degrees just to test the limits. Another update will follow...

  • 0 in reply to Leif Svensson
    Prodigy 20 points

    After replacing the LM5013-Q1 with a new one, exactly the same, everything seems to work just fine! No other changes on the PCB whatsoever. There must have been some issue with just the old one. It was fine when tested in +55C but showed serious trouble in +40C. With the new chip there are no problems even when tested in -45C!

    Well, seems like there was no problem after all. Just a faulty chip.  :-)