TINA/Spice/TPS62125: Simulation of inverting buck-boost topology

M Anand

Part Number: TPS62125
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Hi,

I am considering using the TPS62125 in an application requiring generation of -10V from +10v using the inverting buck-boost topology detailed in this app note:

However, in simulating this circuit with Tina-TI, I am not getting anything like the outputs expected. The attached schematic is the same as the test circuit shown in Fig. 16 of the above app note (which produces -5V from +5V input), but as you can see from the attached simulation results, the output is nothing like a regulated -5V.

It would seem like I am missing something fundamental - any ideas as to what it might be?

Thanks,

Best regards,

Anand.

Minus10.TSC

over 5 years ago

0 Dorian Brillet de Cande over 5 years ago

TI__Genius 14856 points

Hello Anand,

Can you share with us the schematic you have used in TINA TI?

I see an erroneous value in the App note which needs to be corrected.
Did you use a 100 Ohm resistor for the PG pin? This value needs to be 100k.

Thank you very much!
Best Regards,

Dorian

0 M Anand over 5 years ago in reply to Dorian Brillet de Cande

Prodigy 240 points

Hi Dorian,

I believe I had attached the TINA TI schematic in the original email, wonder if it got stripped somehow. Anyway, it is attached to this post again, please let me know if you can't see it.

The PG pin is left unconnected in the design.

Thanks,

Best regards,

Anand.

8176.Minus10.TSC

0 Dorian Brillet de Cande over 5 years ago in reply to M Anand

TI__Genius 14856 points

Hi Anand,

You sent the TINA TI schematic, I just didn't see it.

Please check out this FAQ for more information:

http://e2e.ti.com/support/tools/sim-hw-system-design/f/234/t/692602?tisearch=e2e-quicksearch&keymatch=floating%20ground

Thank you very much!

Best Regards,

Dorian

0 M Anand over 5 years ago in reply to Dorian Brillet de Cande

Prodigy 240 points

Hi Dorian,
I see....based on the FAQ, since I don't see the TPS62125 model explicitly mentioning "inverting," I assume it doesn't support the inverting configuration then?

Is there any way to simulate it?

Regards,
Anand.

0 Dorian Brillet de Cande over 5 years ago in reply to M Anand

TI__Genius 14856 points

Hi Anand,

Unfortunately we have no software which can support this.

This can be replicated easily on the TPS62125-EVM, we have a blog explain how to modify a step down converter to an inverting buck boost topology:

https://e2e.ti.com/blogs_/b/powerhouse/archive/2018/05/16/how-to-modify-a-step-down-converter-to-the-inverting-buck-boost-topology

A reference Design was made on this TPS62125, maybe you can have a look at it too.

http://www.ti.com/tool/PMP9760

Thank you very much!

Best Regards,

Dorian

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TINA/Spice/TPS62125: Simulation of inverting buck-boost topology