LM3488: LM3488 is not switching the MOSFET

Dear Niklas,

Thank you for the nice comments, I already changed them in the file, but I did not see any issue related to the output of the negative voltage.

After I implemented the changes, it seems we have convergence problem, would you please help me fixing this?

Then update TINA file:

8081.LM3488.TSC

Best regards,

Behnam,

Dear Niklas,

Thank you very much for your help, I really appreciate it.

Would you please let me know that should I run steady state simulation or transient? In case of steady state I get the following results:

It shows, HV+=200nV and HV-=-20nV? am I right? it seems too low to me, would you please let me know how we can fix it?

Best regards,

Behnam,

Hello Niklas,

I simulated for a longer time and it seems the voltages are converging to +/- 16.3 v

What, I'm looking for is higher voltages like +/- 70 v, would you please let me know how can I fix it?

Regards

Hi Behnam,

Thanks for the feedback.
I double checked the simulation and it seems like the system is not running stable.

Before we continue debugging the model, can you tell me where you found this reference design and what is the main purpose of this simulation?
Do you just want to validate the behavior of the design through simulation?

Thanks and best regards,
Niklas

Dear Niklas,

I found the reference design here:

https://www.ti.com/lit/an/sloa284a/sloa284a.pdf?ts=1719809380523

Ultrasound Smart Probe Power Supply Reference Design.pdf

I have also attached the PDF file (please see page.14). The purpose of the simulation  is to validate if this design really works?

What is the main purpose of this simulation?

Because previously I have made the design (PCB) and after I got the PCB, it seems that it is not working, so I decided, first by simulation at least I can validate the the refence design to see if it is working?

Do you just want to validate the behavior of the design through simulation? At the moment yes, but I also have the PCB which is not working 

Hi Behnam,

Thank you very much for sending the reference.
I just discovered there is an ongoing thread on the exact same design and simulation.

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1379092/lm3488-pspice-result-discussion-to-generate--80v

I am working on additional simulations to get this design running either in TINA or PSpice and will then post all my findings in the other thread.

Best regards,
Niklas

Hello Niklas,

Thank you very much for sharing this, yes, it is exactly the same issue, would you please let me know if there is any update?

Regards,

Hi Behnam,

Thanks for checking on this.
I just answered the other thread as well.
Debugging the simulation has not lead me anywhere so far. I am afraid this is a simulation error that cannot be fixed within a few days and takes longer time to solve.

I am very sorry for this inconvenience.
Best regards,
Niklas

Dear Niklas,

Thank for all your efforts.

Mu issue with this chip is that I even made a PCB, but the system is not reaching voltages higher than +/- 18V, so would you please let me know if there is an alternative chip that I can use for this purpose? I prefer a chip that I can find easily a working simulation for that.

Regards

Hi Behnam,

Yes, an alternative part for LM3488 is the LM5155.
This device is more modern, has improved features and runs in newest manufacturing process.

Best regards,
Niklas

Dear Niklas,

Thanks for the update.

How about the schematic for achieving variable output voltage from +/-5V to +/-80V,can I use the previous design and just replacing LM3488 with LM5155?otherwise, would you please let me know what should I follow? and how can I proceed with the new chip?

Regards,

Behnam,

Hi Behnam,
LM5155 is a very similar device to LM3488, but much more modern and with improved features.
As the design itself is feasible, you can run a simulation with the LM5155 model and check if the results look better here.

I also found a reference design using LM5155 for a SEPIC design that uses slightly different specs, but should still be useful:
https://www.ti.com/tool/PMP40488

Best regards,
Niklas

Dear Niklas,

I check the design you mentioned, it looks nice, in my application I can live with +/-60 V as well, in case if I want to simulate this reference design:

Considering I can not find the following components libs in TINA-TI, and I have to use some generic MOSFET and diode instead:

PMV213SN,215

MBR2H200SFT1G

Do you think it can have an effect on the simulation result?

Hi Behnam,

The impact of using ideal components for MOSFET and diode should be very small.
Losses and diode voltage drop may not be as accurate, but the device switching and output ramp-up behavior should not be affected.

Best regards,
Niklas