The difference between the Ambient and junction temperature

[santhoshv78]

temperature simulations

What is the difference between the Ambient and junction temperature.
How can I simulate the cmos circuit in Junction temerature.

 

[sunking]

Re: temperature simulations

junction temperature is the temperature of pn juction in the die.
Ambient temperature is the temperature outside the die, suck as package

 

[vomit]

Re: temperature simulations

What is the difference between the Ambient and junction temperature.
How can I simulate the cmos circuit in Junction temerature.

Calculate the power dissipated in your circuit, search for the thermal resistance (degrees per watt) and multiply it with the power to get the temperature rise over room temperature.

The thermal resistance is dependent not only of the package type, but also whether or not cooling airflow is present. For an ASIC the vendor must be able to give that figure to you.

 

[rajesh13]

Re: temperature simulations

junction temperature is the temperature of pn juction in the die.
Ambient temperature is the temperature outside the die, suck as package

Normally, how much is the difference between the juction temperature & ambient temperaure. Because what is specified in the specification is the Juction Temp. & while testing we see(or control) only the ambient temp.

 

[kgl_13gr]

Re: temperature simulations

You can use the equation Tj=Tamb+Pd*Rth
where Tj= junction temperature,Tamb=ambient temperature,Pd=dissipated power and Rth=thermal resistance between the junction and air.
Some more analytical information
**broken link removed**

 

[avinash]

Re: temperature simulations

junction temperature is approximately 10 degree celcius more than the ambient temperature as i use in 0.8u technology.

 

[rajesh13]

Re: temperature simulations

junction temperature is approximately 10 degree celcius more than the ambient temperature as i use in 0.8u technology.

Does that means that it depends upon the technolgy also.

 

[modern_analog]

Re: temperature simulations

Does that means that it depends upon the technolgy also.

It depends only on the power dissapated in the chip. Generally, .8u will be less power hungry and have bigger packages. .13u will be more dense and burn more power so the difference will be more. Again this is all typicl case.