TPS54240 SIM runs, but incorrect results

Walter Brumm

Other Parts Discussed in Thread: TPS54240

Hello,

I received an email stating my previous sim might have suggested a bad operating point, so I'm trying to rerun this.

Since this is an existing marginal design, I'm trying to model it as accurately as possible, using real component values to figure out how marginal the design is. The design I'm trying to simulate uses Y5V output caps, which are quite variable.

My design:

TPS54240

22.5-23.2Vin, 12Vout,

1.5A out

Using the DC bias graph on this post:

https://e2e.ti.com/support/development_tools/webench_design_center/f/235/t/467378

over 8 years ago

0 Walter Brumm over 8 years ago

Prodigy 160 points

I found that a 50V cap has ~94% at 12v. I'm using 4x 10uF Y5V, which correspond to an idea 16uF cap. I also noticed my inductor is rated for 3.48A, while WEBENCH wants 3.5A.

The phase/gain margin appear to be correct, however the SIMs don't appear to run. See the screenshot below--the load transient simulation doesn't change in current:

Is this a bug with the TPS54240 model? Or is WEBENCH only able to simulate 'recommended' designs?

Thanks,

Walt

0 Nikhil Gupta (Product Folder Models) over 8 years ago in reply to Walter Brumm

TI__Mastermind 39210 points

HiWalt,

Can you share your design with us. Please click on "Share Design" on top and create a public share. This will help to debug your problem.

Thanks,

0 Walter Brumm over 8 years ago in reply to Nikhil Gupta (Product Folder Models)

Prodigy 160 points

Hi Nikhil,

Here's a link to the design:
webench.ti.com/.../SDP.cgi

Thanks,

Walt

0 Nikhil Gupta (Product Folder Models) over 8 years ago in reply to Walter Brumm

TI__Mastermind 39210 points

Hi Walt,

We identified the issue and it was fixed last night. Please give it a try again. For your convenience, here is the working design and simulations with your inputs:

https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=B4251A8D5FA5AB60

0 Walter Brumm over 8 years ago in reply to Nikhil Gupta (Product Folder Models)

Prodigy 160 points

Hi Nikhil,

I saw the same problem on Friday (18th) however the simulations worked today without issue.

Thanks!

Simulation, hardware & system design tools

Simulation, hardware & system design tools forum

TPS54240 SIM runs, but incorrect results