UCC28950: OUTC and OUTD failing to switch

Hello,

I am reviewing your inquiry and will get back to you shortly.

Regards,

Hello,

Which Tina model are you using, startup or steady state?

Regards,

Mike,

I'm using the transient model in my own circuit

Edit: It aligns with the startup reference design. Output is the same in voltage and current modes

Hello,

Your inquiry is under review and I will get back to you shortly.

Regards,

Hello,

It appears that the tina transient model is not functional.  I had reported this issue to the PSpice modeling team and it should not have been released.  Please use the tina steady state and startup models.  These have both been tested and verified.

Regards,

Mike,

I assume you're referring to the SLUM276A and SLUM277A files? Both use the transient model for the UCC28950 and work correctly - same model I am using in my TINA file. If you could clarify on this I would appreciate it thanks.

Pic of the functioning UCC28950 transient model in SLUM277A:

Hello,

The model I was referring to was SLUM278A that was not working.  The SLUM276A and SLUM277a files should be O.K.

Regards,

Mike,

I didn't word my previous replies very clearly, I meant the UCC28950 component model itself - not a premade TINA circuit file. 

Regardless I since have gotten the OUTC and OUTD to switch... but only barely. Was wondering if you had any tips on getting it to fully function. Attached a picture of the waveform from 0ms to 24ms. OUTC and OUTD switch off quickly after startup with Vout leveling out at 1.74V - a good several hundred volts under what I designed the output to be. Appreciate the help again

Hello,

The Out C and Out D should be switching.  I wonder if there is not enough resolution.  Some times if there is not enough data points the simulation tools can give erroneous results.  Could you try increasing the amount of data points you are using.  

There is one thing I am puzzled about.  How can you get a current sense signal with out Out D and Out C not switching.  You may want to double check your schematic in your simulation file to make sure there is not any connections not attached correctly.

Regards,

Mike 

Mike,

I'll give the increased resolution a try - that's a good point that I didn't think of thanks

Hello,

I was glad that I could help.

Regards,

Mike

Mike,

Electronic rules check passed. Changing the transient max timestep did alter the current sense output graph - but still not seeing the output that I'm expecting

Hello,

I am reviewing your inquiry and will get back to you shortly.

Regards,

Hello,

Out D and Out F should be switching no matter what.  There is something wrong with the tina device model.

I am going to move this to the TI PSpice team forum so they can help you with this issue.

You might want to try the IT PSpice models for these devices to see if you can the simulation working with the PSpice model vs the tina model.

You can find the TI PSpice model below.  It has both the transient and steady state models in it.

https://www.ti.com/lit/zip/slum169

If you don't have TI PSpice you can down load it for free. 

https://www.ti.com/tool/PSPICE-FOR-TI?keyMatch=PSPICE%20FOR%20TI

Regards

Hello Modeling Team,

This customer is having an issue with the tina models for the UCC28950.  Out C and Out D should be switching when OUT A and OUT B are.

In the real device there is not a point where OUT C and OUT D would not be switching if OUT A and OUT B are switching.

Could someone from your team look into this for us?

Regards and Thanks,

Hey Mike,

There's not really a modeling team. That responsibility belongs with the product line. I'll send you the JIRA ticket for getting the PSpice model published to PSpice for TI so that it can be integrated into the library.

The TINA model should be very similar to the PSpice model as they were both created around the same time.

David

David,

To clarify... is the UCC28950 model not already published for PSPICE? I can check into using pspice instead, but as of right now is there no model support for this component in tina? thanks!

Hi Aidan,

There is a PSpice model, but it is currently only available on the produt folder page. You can download it from there.

We're working to get it into the PSpice for TI tool so that it can be more seemless an operation.

David