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True negative supply

Jared Becker
Genius 11505 points
Other Parts Discussed in Thread: LM2578A, TL5001A, TPS65130, TPS60400, TPS63700

Hi Team,

Do we have a device in our portfolio that is a true negative supply? Something to displace the LTC7149..

Thank you,

Jared

  • 0
    TI__Guru**** 191445 points
    LTC7149 is inverting buck boost. There are many possibilities. Can you post your input voltage, output voltage and current? Then we can select some possible solutions.
  • 0 in reply to JohnTucker
    TI__Genius 11505 points

    Hi John,

    I am looking for something that is properly ground referenced.

    i.e. the LTC7149's ground pin is actually connected to ground:

    I have looked at this link for solutions from our portfolio, but for all our solutions the ground is referenced to the negative supply: 

    Here is why a true negative supply is desired: When a positive switching power supply is connected in the negative configuration, it is possible to have currents that back flow from the output of the supply to the digital interface controlling the power supply. True negative supplies have an interface designed to be connected up to controlling logic with no inversion.

    Here are the requirements trying to be met:

    Input: 24V

    Output: -20V

    Output Current: ~250mA

    Power good feature.

    Looking forward to your feedback

    -Jared

  • 0 in reply to Jared Becker
    TI__Guru**** 191445 points
    You are looking at various older controllers such as LM2578A, LM34063A, TL5001A, TL1491A, etc. I don't think any of them have power good function.
  • 0 in reply to JohnTucker
    TI__Genius 11505 points

    So it does not sounds like we have a inverting power supply where the ground pin is ground referenced, correct?

  • 0 in reply to Jared Becker
    TI__Guru**** 191445 points

    Those were the parts my search revealed.  As a disclaimer, my group would not have anything to offer, but maybe someone else knows of something.

  • 0
    TI__Guru 58225 points

    Hello Jared,

    If you are searching for a part from 24V input voltage, I do not know of any in the portfolio I know, but we have several that are going from +5V to -5V, e.g. TPS63700 or TPS60400. And some that have 2 outputs, one positive and one negative one, e.g. TPS65130

    What is the reason that you want to have the GND pin referenced to the system GND?

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    TI__Genius 11505 points

    Hi Brigitte,

    Thank you very much for the suggestions! The reason I want to have the GND pin referenced to the system GND is based upon what I mentioned above..

    Here is why a true negative supply is desired: When a positive switching power supply is connected in the negative configuration, it is possible to have currents that back flow from the output of the supply to the digital interface controlling the power supply. True negative supplies have an interface designed to be connected up to controlling logic with no inversion.

    Thank you!

    Jared