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Voltage regulator junction temperature.

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Bsr

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I am searching for a voltage regulator which gives output voltage of 3.3V, 2A with input of 7.5V min. I have seen Voltage regulator which has the junciton temperature range like 0 to 125 degree celsius.

there is calculation for junction temperature related to that particular regulator which I got is 170 degrees celsius related to my case . But the max junction temp of regulator is 125 C. Is it okay to use this regulator ?

Note: Here in my case the current of 2A flows only once for every 1 Min.
 

Are you saying you want to run your regulator at 175 degrees even though it's maximum rating is 125? Why would you think this is ok? You are dissipating about 8 watts across this device, you need some kind of heat sinking. A LOT of heat sinking.
 

not exactly @ 175 degree celsius . but above the junction temperature around 150 C.. but In my case The load will take 2A of current once for every minute , I mean not a continuos supply . So does it make problem in this case also ?
 

Hi.

The simple answer is: don't run the regulator with a junction temperature of 125°C or above.

If the power consumption is short enough that the temperature doesn't touch this limit .... It is OK.

Klaus
 

What does "once for every minute" mean? Is it on for 59 seconds for each minute, or 1 femtosecond per minute? That makes a big difference.
 

Raising the junction temperature above about 150 °C triggers thermal shutdown.

The other point is that thermal cycling is the dominant wear mechanism for power semiconductors (provided you are keeping maximum voltage and current ratings). Roughly each 10 degree more halves the lifetime.
 

This application really wants a switcher. Unless you need
your 2A to be RF / data acq grade kind of quiet.
 

The other point is that thermal cycling is the dominant wear mechanism for power semiconductors (provided you are keeping maximum voltage and current ratings). Roughly each 10 degree more halves the lifetime.
Click to expand...
Thanks, this is applicaable to Bsr's case where he goes on and off regularaly, so his thermal cycling is extreme.
I take it that that is what is meant by thermal cycling.
I must admit i have tried to find literature on the web about thermal cycling being a failure mode of power semiconductors but cant find anything. I will try to find it for Bsr.

Bsr can also utilise good PCB heatsinking, thermal via'ing etc to get the temperature down...or Bs could switch a fan on the reg for the short time that its on.
What about a peltier cooler.

...second thoughts...a simple buck converter sounds what Bsr really needs.
You can buy buck converters on a chip from linear.com that will do what Bsr wants.
 

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