TIOS1023: Thermal resistance

Hello Jonathan, 

Thank you for your comment. 

Using a PCB thermal calculator, I think we can estimate the junction temperature of TIOS1023 DRC package using LDO with similar package but how about YAH package? 

There is no reference with DSBGA package. would you please let me know your opinion how can we estimate the junction temperature of YAH package? 

Thank you.  

Hello Dino,

Ok yes, there is less information available for devices with this type of package.  I would probably have to submit a request for this to be simulated with a custom board size and stackup (layer count, number of vias, etc.).

Can more details be provided about the board, or perhaps a set of gerbers that can be used to generate the model?  These can be shared directly without using this public forum.

Also out of curiosity, does the customer have the ability to run their own thermal simulations if a Delphi compact thermal model could be provided?

Regards,

Jonathan

Hello Jonathan, 

Thank you for your comment. 

Jonathan Nerger said:

Can more details be provided about the board, or perhaps a set of gerbers that can be used to generate the model?  These can be shared directly without using this public forum

- Their board concept is not fixed. 

- Board size 4.8x10mm, 4 layer, The other conditions are the same as the condition that get the results  "YAH package 79.3°C/W" from datasheet.  

Is it possible to submit a request with above condition? If possible, please simulate also 3.2x6.5mm board size.

Jonathan Nerger said:

Also out of curiosity, does the customer have the ability to run their own thermal simulations if a Delphi compact thermal model could be provided?

I don’t know much about a Delphi compact thermal model , but I don’t think the customer would be able to use it. Is it available to share user guide of a Delphi compact thermal model? 

Thank you. 

Hello Dino,

Please confirm what the layer order is for the 4 layer board with regards to signal and power/ground planes.  I'm assuming the top and bottom are signal layers with the internal layers being a power and ground.  Because the amount of copper makes a difference in thermal models, this information is usually needed.

I will also need to know their expected power dissipation and ambient temperature for their application if they can provide this.

I too am not skilled in thermal modeling, but the term Delphi refers to the type of compact thermal model that can be shared without an NDA unlike detailed thermal models that reveal internal details of the package and material properties.  I've seen these requested by customers that want to run their own thermal model simulations.

Regards,

Jonathan

Hello Jonathan, 

Thank you for your comment. 

You are correct. the top and bottom are signal layers with the internal layers being a power and ground. 

Jonathan Nerger said:

I will also need to know their expected power dissipation and ambient temperature for their application if they can provide this.

Their expected power dissipation is 0.365W, 100mA load current, 30V to 3.3V /12mA LDO output. 

Thank you. 

Hello Dino,

Thanks.  I will try to get an analysis run with this information.

Regards,

Jonathan

Hello Jonathan, 

Is there any progress regarding thermal analysis? 

Please let me know your opinion if you have any progress. 

Thank you. 

Hello Dino,

The simulation request in in the system, but there are many other requests before it in the queue and the job has not started yet.  It usually takes a couple of weeks to get results from a request.

Regards,

Jonathan

Hello Jonathan, 

Thank you for your reply. 

If you get simulation results, let me know 

Thank you. 

Hello Dino,

Yes, I will let you know as soon as I receive the results.  Unfortunately there is only a small team that is responsible for all thermal model requests for the company and so it can take a little time to get results.

Regards,

Jonathan

Hello Jonathan, 

Is there any progress regarding thermal model request? 

Please let me know if you get any feedback. 

Thank you. 

Hello Dino,

Thanks for the reminder email as I had not checked the status since returning from the recent US Thanksgiving Holiday.  I saw that the analysis simulations were still not complete, but that the engineer had put in a comment requesting additional information be provided about the specific board layout and boundary conditions. 

Because I know the customer has not done a layout yet, I followed up directly with him through email and asked what specifically he needed, or if he had any other suggestions on how to answer the customer's core question as follows.

Nam, Dino said:

2. Could you calculate RθJA for customer board size (4.8x10mm )? How can estimate thermal resistance for customer board? 

The concern with this type of simulation is that if he just assumes that size of board is floating in air the temperatures will get very high.  He could run simulations of that but it would give unrealistic results.  Adding boundary conditions (i.e. fixed temperature at certain locations, other cooling mechanisms) would help refine the simulations.

Alternatively,  he suggested they could calculate the approximate junction temperature if they know their peak board temperature and the power dissipation based on the Psi-JB value.

More info can be found in the Semiconductor and IC Package Thermal Metrics Application Report (Link) which is linked in the datasheet's Thermal Information table footnote.

The datasheet does provide Psi-JB for the YAH package device.

I assume this small board will be embedded in some sort of metal enclosure like the following image, or in something that will have some sort of ambient temperature or heat sinking function that will help hold the PCB at a more known temperature.  As it stands with the current request is that there is no defined PCB temperature or heat sinking functional reference to create a somewhat "fixed" or known reference to calculate the difference between the IC temp and this reference temp.

Hopefully the customer can find the Psi-JB method useful with various estimated PCB temperatures.  Otherwise, can they provide the additional boundary conditions I have mentioned (i.e. fixed PCB temp at certain locations or other cooling mechanisms that will be acting on the PCB)?

Again, sorry for not checking this again a week ago.

Regards,

Jonathan

Hello Jonathan, 

Thank you for your strong support. 

As I mentioned before, There is no real board so we can't check PCB temp and other boundary condition. 

The customer are only reviewing their concept with customer board size (4.8x10mm ). 

Jonathan Nerger said:

The concern with this type of simulation is that if he just assumes that size of board is floating in air the temperatures will get very high.  He could run simulations of that but it would give unrealistic results.

I think also it would be unrealistic results and I think the thermal resistance (RθJA ) would be over 500°C/W

Although the simulation result is unrealistic results, please let me know simulation result with board condition. Based on the simulation result,  I will push the customer they have to reduce their application current consumption(<3mA) and power dissipation(<0.1W).

Please let me know your opinion. 

Thank you 

Hello Dino,

Since the customer can't provide any additional information about how this board will mounted, I'll request the simulations be run with whatever assumptions the thermal engineer thinks are best.

Regards,

Jonathan

Hello Jonathan, 

Thank you for your support. 

Good, please let me know the result with test condition whatever assumptions the thermal engineer thinks are best.

The test condition which the thermal engineer thinks are best would be also good point for customer design to reduce thermal concern. 

Thank you. 

Hello Dino,

I will update you after hearing back from the Thermal Engineer.

Regards,

Jonathan

Hello Jonathan, 

I am very appreciate for your great support. 

It is good reference for customer design. 

Thanks again. Have a good holiday.

Regards, 

Hello Dino,

Thank you, and I wish you happy holidays as well.

Regards,

Jonathan