Hello,
I'm calculating the allowable maximum power dissipation of DS26C31T but I'm not able to find the junction temperature of the IC. In the datasheet storage temperature is given. Can you please explain me the difference between the storage, operating and junction temperature for TI. Please guide me for the value of junction temperature also.
Hi Nisha,
Max power dissipation at 25C is listed in the absolute maximum ratings table - with the specific deratings for ambient temperatures greater than 25C is listed in note 4. All of these are shown in the picture above.
These are the values you should be using for your power dissipation calculation.
That being said the difference between operating temperature, junction temperature, and storage temperature can be seen below:
Operating temperature - this is used to refer to ambient environmental temperature - i.e. what is the air temperature around the device during operation. We qualify our devices within a specific ambient temperature range - for the "T" variant of this device is qualified between -40C and 85C. This is the range in which we guarantee datasheet specifications.
Junction temperature - if included in datasheet you will see this called either junction or virtual junction temperature (effectively they are the same thing - but virtual junction is a way to treat a multiple junction device as a single value). This is basically the temperature of the silicon die during operation. If a device doesn't give max power dissipation - this one does give that - the junction temperature + thermal resistance can be used to approximate max power dissipation.
TJ = TA + P_tot * R_theta_JA(effective) --> P_tot = (TJ-TA)/R_theta_JA(effective)
On this device however we only give P_tot - which is what I included at the top of this reply so that should be used.
Storage temperature - this is the temperature range at which the die can be stored, which means its not being powered or in system, without damage. This is tested by temperature cycling the device at both extremes multiple times and then it is tested to see if it still works. The biggest difference between storage temperature and junction temperature is that junction temperature is referring to when device is powered up and storage refers to device when its not. Generally speaking though max storage and max junction are usually pretty similar if not equal.
Best,
Parker Dodson
