Hello Everyone,

Hope you are doing well.

I am using Mosfet CJ31339KDW-G for my design.
My power dissipation for this device is 10mW.

Now, How do I calculate derating of Mosfet.
How do calculate life time of Mosfet.
How do I calculate temperate rise of Mosfet.
how to estimate life of Mosfet for every degree rise in temperature.

Thanks !!!

 

I cannot find this MOSFET on the internet.

 

I am using Mosfet CJ31339KDW-G for my design.

A Google search on that part number gives zero results.

When asking a question about a specific electronic part, PLEASE post a link to the part's online datasheet, or upload the datasheet itself as an attachment to your post. Otherwise, in cases such as this, you are wasting our time.

My power dissipation for this device is 10mW.

If your power dissipation is only 10 milliwatts (0.01 watt), you need not worry about temperature rise or lifetime: even worst-case, with a SOT-23 SMT package, the junction-to-ambient thermal resistance is probably less than 500 °C/W so the temperature rise at Pd=0.01W will be no more than 5 °C. For power MOSFETs in larger cases, such as a TO-220 case, the thermal resistance (and consequent temperature rise) is even less. In either case, the temperature rise will be so low as to have little, if any, effect on device lifetime.

As for the rest of your questions, read the Wikipedia articles on Thermal Resistance and Power Derating. They explain all, and the datasheet for your MOSFET will give you the thermal resistance and power derating parameters you need to do your calculations. Those calculations are simple and shouldn't require explanation.

 

I cannot find this MOSFET on the internet.

Sorry it was mistaken. Typo error.
Below was the part no

CJ3139KDW-G
https://www.mouser.in/ProductDetail/Comchip-Technology/CJ3139KDW-G?qs=/ha2pyFadujSfJbbETfsFMsMpxvMz8bMdm4/qxyvoEMa0dvnsOLa/Q==

 

A Google search on that part number gives zero results.

When asking a question about a specific electronic part, PLEASE post a link to the part's online datasheet, or upload the datasheet itself as an attachment to your post. Otherwise, in cases such as this, you are wasting our time.


If your power dissipation is only 10 milliwatts (0.01 watt), you need not worry about temperature rise or lifetime: even worst-case, with a SOT-23 SMT package, the junction-to-ambient thermal resistance is probably less than 500 °C/W so the temperature rise at Pd=0.01W will be no more than 5 °C. For power MOSFETs in larger cases, such as a TO-220 case, the thermal resistance (and consequent temperature rise) is even less. In either case, the temperature rise will be so low as to have little, if any, effect on device lifetime.

As for the rest of your questions, read the Wikipedia articles on Thermal Resistance and Power Derating. They explain all, and the datasheet for your MOSFET will give you the thermal resistance and power derating parameters you need to do your calculations. Those calculations are simple and shouldn't require explanation.

Sorry for inconvenience caused to you.
https://www.mouser.in/ProductDetail/Comchip-Technology/CJ3139KDW-G?
qs=%2Fha2pyFadujSfJbbETfsFMsMpxvMz8bMdm4%2FqxyvoEMa0dvnsOLa%2FQ%3D%3D

 

A Google search on that part number gives zero results.

When asking a question about a specific electronic part, PLEASE post a link to the part's online datasheet, or upload the datasheet itself as an attachment to your post. Otherwise, in cases such as this, you are wasting our time.


If your power dissipation is only 10 milliwatts (0.01 watt), you need not worry about temperature rise or lifetime: even worst-case, with a SOT-23 SMT package, the junction-to-ambient thermal resistance is probably less than 500 °C/W so the temperature rise at Pd=0.01W will be no more than 5 °C. For power MOSFETs in larger cases, such as a TO-220 case, the thermal resistance (and consequent temperature rise) is even less. In either case, the temperature rise will be so low as to have little, if any, effect on device lifetime.

As for the rest of your questions, read the Wikipedia articles on Thermal Resistance and Power Derating. They explain all, and the datasheet for your MOSFET will give you the thermal resistance and power derating parameters you need to do your calculations. Those calculations are simple and shouldn't require explanation.

How do you say temperature rise is no more than 5 degreeC.
and the temperature rises in mosfet

 

How do you say temperature rise is no more than 5 degreeC.
and the temperature rises in mosfet

If the thermal resistance is, for example, 500 °C/W and you are dissipating 0.01 W, the temperature rise will be:

Δt = 0.01W * 500 °C/W = 5 °C above ambient.

The datasheet you linked shows the following information:

Here, the junction-to-ambient thermal resistance is listed as 833 °C/W, so if you're dissipating 0.01 W the temperature rise above ambient would be 8.3 °C.

Simple multiplication, nothing more.

 

If the thermal resistance is, for example, 500 °C/W and you are dissipating 0.01 W, the temperature rise will be:

Δt = 0.01W * 500 °C/W = 5 °C above ambient.

The datasheet you linked shows the following information:
View attachment 176360
Here, the junction-to-ambient thermal resistance is listed as 833 °C/W, so if you're dissipating 0.01 W the temperature rise above ambient would be 8.3 °C.

Simple multiplication, nothing more.

Thanks for your information.!!!

Thats correct i understood.
What would effect in mosfet if temperature rise is 8.3 °C.
What is acceptance criteria for temperature rise.
or what is significance.

Regards,

 

What would effect in mosfet if temperature rise is 8.3 °C.

What do you think it would be? Does an 8.3 °C seem like a lot to you? Would you even be able to feel it if you touched the part with your finger? THINK.

What is acceptance criteria for temperature rise.

It says right there in the datasheet, under "Junction Temperature Range." The maximum allowable junction temperature is 150 °C. Multiply the thermal resistance (833 °C/W) by the power dissipation (0.01 W) to calculate the temperature rise (8.3 °C), add the calculated temperature rise to the ambient temperature (25 °C) to get the junction temperature (33.3 °C), and the result must be less than 150 °C. It is, so the MOSFET is safe.

That's all there is to it, no more than that. So simple a child could do it.

 

What do you think it would be? Does an 8.3 °C seem like a lot to you? Would you even be able to feel it if you touched the part with your finger? THINK.


It says right there in the datasheet, under "Junction Temperature Range." The maximum allowable junction temperature is 150 °C. Multiply the thermal resistance (833 °C/W) by the power dissipation (0.01 W) to calculate the temperature rise (8.3 °C), add the calculated temperature rise to the ambient temperature (25 °C) to get the junction temperature (33.3 °C), and the result must be less than 150 °C. It is, so the MOSFET is safe.

That's all there is to it, no more than that. So simple a child could do it.

Thank you so much for your valuable time and reply.

A novice in electronices with burning desire to learn could be a child ..

I am able to solve the math equation. I used to get highest marks in math.

My intention was to understand the concept of thermal rating , derating of device.

Regards,

 

Thank you so much for your valuable time and reply.

A novice in electronices with burning desire to learn could be a child ..

I am able to solve the math equation. I used to get highest marks in math.

My intention was to understand the concept of thermal rating , derating of device.

Regards,

Most people don't worry about the life of a single FET because it is in the giga hours.
From what I have read there is about 1 order of magnitude difference from nominal temperature to maximum temperature.