UC1834J

Hello Jesus

This is a very versatile part that can be used in many configurations.  The actual power that is dissipated in the part would of course depend on the actual current draw from all ports in a given application summed together.  Once the power  across the part is calculated you will need the thermal resistance or derating factor to make sure that the package does not over heat - I think that this is what you are asking for?

Fortunately, package thermal characteristics are not part dependant.  I found this in formation in the data sheet for the TL1452, where on page 3 you will find the derating information that I believe that you are looking for (for the J package).

Regards

Bill

Hello Bill,

Yes I am looking for the thermal resistance. I understand that the thermal resistance will vary depending on the application. But I am trying to find the general min and max of that resistance, without taking into effect the application.

I hope this makes sense.

Thank you,

Jesus

Jesus,

I think that the Derating Factor for the "J" package is a good general number to be used for thermal calculations - and note that the Derating Factor is the reciprocal of the Thermal Resistance, theta_ja, between the ambient air temperature and the worst case semiconductor junction temperature. And so, based on the data found in the TL1451 data sheet the theta_ja = 1/Derating Factor = 1/11mW/degC = 90.9degC/Watt.  I apologise for any mis communication. 

I find that thermal information is notoriously unsatisfying - especially "theta_ja" which is so dependant on the size of the copper area to which the part is attached. At Texas Insturments the amount of copper is in accord with some JEDEC standard PCB layout. But it is worth noting that the theta_ja does vary with the amount of copper area attached but probably less so for a leaded part with no heat tab.  Also note that a good estimate for thermal resistance to the top center of the package, Theta_jc, is approximately 60% of the theta_ja value. 

(The worst case junction temperature is Tj=Tambient+(Theta_ja*Pd).  The junction temperature is determined by the ambient temp, Tambient, the thermal resistance, Theta_ja, and the dissipated power in the part, Pd.)

Regards

Bill

Hello Bill,

We tested the parts at different temperatures with an voltage of 2V, the results we not consistent to that of the "J" package for the TL1451 specs. At -25 to -45 degrees the stability of the IC was very inconsistent, as for the 25 to 125 degrees the IC stayed stable without major fluctuation.

Could you explain the reason behind the instability of the test in cold temperatures?

Thank you,

Jesus