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LMZM33604: Inverting Buck Power Supply IC

Meghla Maji
Prodigy 70 points
Part Number: LMZM33604
Other Parts Discussed in Thread: LM25116, LM5116, LM5088, LM25088, , LM5157, PMP23241

Tool/software:

Hi TI Team,

We want to design design power supply DC DC converter for input voltage 12V output voltage -13.5V with 1A output current capability.

  • For generating 12V to -13.5V DC, the TI Power Designer suggested using inverting buck-boost converters such as LM25116, LM5116, LM5088, and LM25088. However, the datasheets for these parts do not explicitly mention support for negative or inverting voltage outputs. While the LMZM33604 supports inverting applications, its 16x10mm size does not fit our requirements.
  • Could you please confirm if there are any other smaller-sized inverting DC-DC buck regulators that can generate -13.5V from 12V?

--

Regards,

Meghla

  • 0
    TI__Genius 9460 points

    HI Meghla,

    Any buck can be used in an IBB configuration. 

    Here's an app note to help - https://www.ti.com/lit/an/snva856b/snva856b.pdf

    Any device rated for 36V would work here, please check out our portfolio and pick the device that meets your size requirements.

    Regards,

    Rahil

  • 0 in reply to Rahil Ajani
    Prodigy 70 points

    Hi Rahil,

    Thank you for the response.

    For our application, we need to convert an input voltage of 12V to an output voltage of -13.5V. To achieve this, would it be best to use a boost or buck DC-DC converter in inverting mode, as per the application note provided?

    From my understanding, since we're converting 12V to a higher absolute value of -13.5V, it seems appropriate to use a boost converter in inverting mode.

    Could you please confirm if this approach is correct?

    Thanks again for your guidance.

    --

    Regards,

    Meghla

  • +1 in reply to Meghla Maji
    TI__Genius 9460 points

    Hi Meghla, 

    Your understanding is correct. I would recommend using a boost converter for this application. 

    Regards,

    Rahil

  • 0 in reply to Rahil Ajani
    Prodigy 70 points

    Hi Rahil,

    Thanks for the response.

    We’ve selected the LM5157 boost regulator to convert an input voltage of 12V to an output of 13.5V. However, we would like to use it in inverting mode to achieve an output of -13.5V.

    The application note you shared earlier explains how to convert a buck regulator to an Inverting Buck-Boost (IBB) configuration. Could you confirm if the same application note applies to converting a boost regulator to an IBB configuration? Alternatively, if there’s specific documentation for inverting boost configurations, please share.

    Thanks again for your guidance!

    Best regards,

    Meghla

  • 0 in reply to Meghla Maji
    TI__Genius 9460 points

    Hi Meghla,

    I'm assigning this thread to the boost team. Someone on their team should be able to help you with this.

    Regards,

    Rahil

  • 0 in reply to Rahil Ajani
    TI__Guru 58581 points

    Hi Meghla,

    please have a look at our reference design database for examples on how to generate a negative output voltage:

    TI Reference Designs Library

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    Prodigy 70 points

    Hi Stefan,

    Thank you for your response.

    We are exploring the TI reference design PMP23241, where the LM61495QRPHRQ1 buck regulator is used to convert an input voltage of 9V to 18V to an output of -7.5V to -12V. Based on this design, it appears that the regulator can operate as a boost in inverting mode, for example, converting 9V input to -12V output.

    Could you please confirm if this regulator can be controlled as an inverting buck-boost to meet our requirement of converting 12V input to -13.5V output? Additionally, would this configuration be suitable for our application?

    Additionally could you please check if there is any DC-DC converter which can directly convert 12Vin to -13.5Vout without using it in inverting mode?

    Thank you for your assistance!

    Best regards,

    Meghla