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TPS62913: Inverting low noise power supply

Seba S.
Prodigy 50 points
Part Number: TPS62913
Other Parts Discussed in Thread: TPS54335A, TPS65131, LMR33630

Dear all,

can the TPS62913 be used to create a negative output voltage / inverting power supply like described in SLVA317B?

I would like to design a very low noise +/- 12V dual / split-rail supply and was wondering whether the TPS62913 can be used to design such a power supply (15-20V input) or would you rather suggest to use another regulator such as the TPS54335A followed by a ferrite bead and a LDO regulator (ultra low noise and output ripple are the most important aspects)?

Many thanks,

Sebastian

  • 0
    TI__Expert 4645 points

    Sebastian,

    Thanks for your question.  Yes, the TPS62913 is a great choice for a low noise inverting buck boost solution.  However, the difference between the input and output voltage must be less than the max voltage rating of the input, which is 17V.  So in this case, it would not be appropriate.  However, if you have a need for a +/-5V, or a 12V input and -3.3V output, those would be possible. 

  • 0 in reply to Steve Schnier
    Prodigy 50 points

    Dear Steve,

    many thanks for your answer.

    Which alternative buck converter from you product portfolio would you recommend for my envisaged application? Main design target is an ultra clean output voltage, with the following specifications: 15-20V Input, +/- 12V Output and at least 0.7A output current per channel.

    Would you rather recommend to use a) an alternative buck converter from your portfolio to generate +/-12V directly from the input (which one would fit best in your opinion?) or b) use the TPS62913 to generate 5V and then use the TPS65131 to generate +/-12V (plus a ferrite bead and a low noise LDO)?

    Many thanks for your advice,

    Sebastian

  • 0 in reply to Seba S.
    TI__Expert 4645 points

    Sebastion, 

    If you have a need for a 5V rail in your application, you can do as you suggest.  However, if you only need +/-12V from the 15-20V input, then you can use WEBENCH to help create the initial step-down, and then the inverting buck boost.  One potential solution for the 12V to -12V IBB is here: https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=DE4ACEC09B0E8CC0. 

  • 0 in reply to Steve Schnier
    Prodigy 50 points

    Dear Steve,

    many thanks for your advice and the recommendation for the LMR33630, which seems to be exactly the converter which I was looking for. I really like that it can be very easily applied with a limited number of external components...

    In order to generate the +/-12V voltage, would you recommend a design with a coupled inductor like shown in SLVA369A or would you rather recommend to two LMR33630s (one configured to generate +12V and the other one configured to generate -12V)?

    Many thanks,

    Sebastian

  • 0 in reply to Seba S.
    TI__Expert 4645 points

    Sebastion, 

    There are a few different ways to accomplish a +/-12V output from a 15-20V input.  If the loads are similar between the +12V and -12V, then a coupled inductor will work.  Keep in mind that any transients on one output rail will be seen on the other output.  If the loads are different, then two separate converters can be used.  Additionally, if the load on the positive rail is low, it is possible to use a lower current converter, as it doesn't require the derating that the inverting buck boost topology does to not hit the current limit.