LM5117: Simulation Convergence Problem

Michele Faini

Part Number: LM5117
Other Parts Discussed in Thread: TINA-TI, CSD19536KTT

Tool/software:

Hi all,

I'm simulating an High Current DC-DC based on LM5117 but I got a lot error message for convergence failed.

I start with the Excel File (attached) for Quick Starting and then I passed to the TINA-TI simulator.

I opened the "snvm619a.tsc" TI base project and I changed step by step all the components to reach the schematic I wanted.
On every change step, I launched the simulation to be sure It worked fine... until I added the TI MOSFET "CSD19536KTT" and the things got wrong.

I tried to change the Analysis Parameters, increase the Shunt Conductance as suggested in the TI web forum, but without success.

I tried to increase the Error percentage of DC and TRANSIENT, but nothing...

Please could you help me? I have no idea to solve this problem and I have to close this project as soon as possible and start to build a test PCB board.

Thank you in advance,

Michele Faini

LM5117 Simple Constant Voltage.tsc CSD19536KTT_TI.TSM Simulation1 - LM(2)5117_quick_start_hv_calculator V1.5.xls

4 months ago

0 EricLee 4 months ago

TI__Guru 61581 points

Hello Michele

There has been a problem when simulating CSDxxxx model and I am not in charge of CSDxxxx device.

Would you please simulate with the default MOSFETs in snvm619a ?

-EL

0 Michele Faini 4 months ago in reply to EricLee

Prodigy 40 points

Hi Eric,

The default Mosfet used in snvm619a is a low current device with high Rds-on and I can't use it because in my project the current is very very high (250 Amps) and I can't reach my result if I use a different Mosfet.

So, I opened a new TINA-TI file, to test only the CSDxxxx device, switching it on and off @250KHz and It works properly! So I think there is no issues about CSDxxxx Tina-TI Model. The problem comes out when I use the Mosfet with LM5117. Any other ideas?

0 EricLee 4 months ago in reply to Michele Faini

TI__Guru 61581 points

Hello Michele

Yes, you are correct. LM5117 model works with other MOSFET models, but the convergence error pops up when using together with CSDxxxx models.

-EL

0 Michele Faini 4 months ago

Prodigy 40 points

Hello Eric,

I tried to use the default Mosfets used in snvm619a in my simulation but the TINA-TI gives the same convergence error.

I don't know how to do this simulation! I thought to semplify the circuit but alle the component are necessary for the correct working of DC/DC.

I tried to use another MOSFET by Infineon... the same error!

Can you help me to find what goes wrong?
I attach the TINA file.
Thanks, Michele

7485.LM5117 Simple Constant Voltage.tsc

0 EricLee 4 months ago in reply to Michele Faini

TI__Guru 61581 points

Hello Michael.

It works well if I start from snvm619. Please try this

snvm619a _ModifiedByEL.TSC

-EL

0 Michele Faini 4 months ago in reply to EricLee

Prodigy 40 points

It seems working. I tried to replace the standard MOS with Infineon High Current MOSFET and works!
Now I'll add other components to implement a Constant Current Controller...
Thank You very much!
Michele

0 EricLee 4 months ago in reply to Michele Faini

TI__Guru 61581 points

Thanks for choosing TI. Please feel free to contact us if you have any question.
-EL

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LM5117: Simulation Convergence Problem