TPS54561: TPS5461 inverting configuration - Pspice simulation

Samuele Di Fabio

Part Number: TPS54561

Hi everyone,

I'm trying to configure the step down TPS54561 in its inverting output voltage mode(Create an Inverting Power Supply from a Step-Down Regulator (Rev. B)) and i'm simulating it in OrCad Capture trough the model available in TI website. Now when simulating the Soft Start node doesn't rise more than 100 mv and after 100 us drops to zero. I'm setting the soft start time to 1 ms. As you can imagine the output voltage doesn't rise to its final value(-18V), starting from a Vin = 24V. So the question is about if the Pspice model is able to simulate the inverting configuration. In the positive voltage mode instead the model works very well.

Thanks in advance,

Samuele.

over 3 years ago

0 Arief Hernadi over 3 years ago

TI__Mastermind 23815 points

Hi Samuele,

The model may not be able to support the inverting configuration due to the internal node is being referenced to a global ground or zero source. One way to get around it is to place the supply in between VIN and VOUT as shown in this article page 9
https://www.ti.com/lit/an/snva856a/snva856a.pdf?ts=1618844628241&ref_url=https%253A%252F%252Fwww.google.com%252F#:~:text=The%20buck%20converter%20takes%20a,connection%20between%20input%20and%20output.

Thanks

-Arief

0 Samuele Di Fabio over 2 years ago in reply to Arief Hernadi

Prodigy 20 points

Hi Arief,

I think that it worked. Now the soft start node rise over the entire soft start period and also the output seems rising. One last thing. Obiousvly if i measure the Vout node with a voltage marker i get a positive voltage, but it's fine in this case beacuse at the end we have Vin + Vout = 42 V. To see the negative voltage i've used a differential voltage marker with positive marker linked to ground and the negative one to Vout.

Thanks for the help.

Samuele.

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TPS54561: TPS5461 inverting configuration - Pspice simulation