This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS56221: Inverting Buck-Boost for split-rail output

Part Number: TPS56221
Other Parts Discussed in Thread: TINA-TI

TI,

I had been exploring the forum for new components I'd like to try out soon, and I was looking at putting together a simulation for the TPS56221 in an Inverting Buck-Boost topology. Similar to this Application note for the TPS6215x  http://www.ti.com/lit/an/slva469c/slva469c.pdf . I'd like to have a solution with a transformer or coupled inductor topology if possible. Is there any reason that this cannot be done with the TPS56221? Any specific 'gotchas' or things I should look out for when trying to design in this way?

Do you have a TI-TINA simulation that already implements this topology for this device or similar?

Thanks.

  • Brian,

    I can't think of any reason why TPS56221 could not be used as an inverting buck-boost. One thing is there is a limited conversion range as Vin - (-Vout) cannot exceed 14 V, so you would be limited to applications like +5 V to -5 V. As far as simulation, there is probably not really an option for it. Every TINA-TI model I have used (unless specifically labeled as inverting buck-boost or negative output) will have the internal GND nodes internally hard tied to GND. For inverting buck-boost, the GND of the IC must be connected to minus Vout.
  • , I appreciate the quick reply. +5/-5 is exactly what I was looking to do. So that seems promising.

    I was playing around with "back of the napkin" calculations using that app note I mentioned before. -- is it true that increasing the the switching frequency will lower the possible output current?

    I was looking at using a 0.45uH coupled inductor since I have that on-hand at the default 500kHz SW. but since its selectable I wanted to explore what a 300kHz and a 1MHz SW would look like.

    Im also investigating what kind of schottky diodes I could actually use that could tolerate the high current in the application, any recommendations?

    Thanks
  • Brian,

    Increasing the switching frequency will lower the p-p inductor current so you should nominally get more load current with higher frequency. Can you show a example of your calculation?

    How high is your current? You may have to parallel the diode.
  • Brian,

    I will close this thread out for now. You can re-open it at any time.