LP2950 TO92 thermal power dissipation

Ravi Bhat1

Hi,

I am new to the topic of thermal dissipation relating to LDOs and appreciate advice on below.

In an application, I am using LP2950-50 (my application uses 12v input and 5V output from regulator) TO-92 package to supply regulated voltage to LCD back-light. I am looking to drive a current of 60mA to LCD back-light load. LP2950-50 regulator is mounted vertically and open to air (within an enclosure), without any thermal shield.

At this load current, when I physically touch the regulator it is quite hot (unfortunately don't have a temperature sensor handy).

From calculation power dissipation is about ~0.42W ( (12v-5v)*60mA).

I would appreciate any advice on if I am operating the regulator in safe thermal limits.

Regards,

Ravi

over 12 years ago

0 Avi Chami1 over 12 years ago

Mastermind 7395 points

It all depends on what is your max. operating ambient temperature. The temperature raise of the device over Tamb is P x Rth, where Rth is the thermal resistance. For the device you used it is 140 deg/W, so for 0.5W, for example, you would get a junction temperature of around 100 degrees. According the datasheet, you cannot surpass 125, so you are running hot but still OK. The question, again, is what will be your max. ambient temperature.

0 Ravi Bhat1 over 12 years ago in reply to Avi Chami1

Prodigy 20 points

Thank you very much Avi for the help. Now I understand this calculation and spec interpretation.

Regards,

Ravi

0 Avi Chami1 over 12 years ago in reply to Ravi Bhat1

Mastermind 7395 points

You are welcome!

I am glad I could help

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LP2950 TO92 thermal power dissipation