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TPS22990: Two TPS22990 hooked to the same output

Hossam Moghrabi
Intellectual 360 points
Part Number: TPS22990

Tool/software:

Hello 

please check the schematic here: https://slow.pics/F822FQQz/

I have 2xTPS22990 devices to have 3.3v and 5v inputs, then both of them connected to the same output so that the user selects the required voltage from a slide switch.

the slide switch delivers 3.3v to the ON pin of the device chosen. while both ON pins are pulled down to ensure they stay off by default.

kindly check this circuit and inform me if it is good and has no problem.

I know there are other specialized ICs for power switching but none has the small Ron this one has as well as the cheap price. I will choose the one with quick discharge to further make it better.

thanks 

  • 0
    TI__Mastermind 31561 points

    Hello Hossam,

    You want to impalement Oring of two power supplies.

    For Oring, you need reverse current blocking, which is not there in TPS22990. 

    Let me know if I am missing any detail here. Below is Ideal diode and Oring portfolio from TI.com

    https://www.ti.com/power-management/power-switches/ideal-diodes-oring-controllers/products.html

    Thanks

    Amrit 

  • 0 in reply to Amrit Jit
    Intellectual 360 points

    hello Amrit,

    well, not exactly that alone. I want the ability to choose between 2 power supplies either 3.3v or 5v, which the output becomes the rail named "3.3v\5v", then the ability to connect or disconnect that rail.

    the suggested ICs didn't really match what I want + they are pricey and high Ron (will generate heat and voltage drop). there won't be any case where voltage will be fed back to the IC so is there a problem which requires reverse polarity protection?

    I tried "power mux" category and the max device supports only 4 amps while I need at least 6. plus, i tried it once and didn't succeed.

    can you check my solution based on this post after clearing my goal?

    I can use other supportive ICs for sure, just that they should be cheap (available at LCSC).

    thanks

  • 0 in reply to Hossam Moghrabi
    TI__Mastermind 31561 points

    I will check and let you know any load switch solution.

    Can you let me know how much units you need for this application?

  • 0 in reply to Amrit Jit
    Intellectual 360 points

    hello

    probably 100-300 units or so. project is still being designed.

    thanks 

  • 0 in reply to Hossam Moghrabi
    TI__Mastermind 31561 points

    Hello Hossam,

    TPS2521xx can be used as PMUX. You can also check TPS25974.

  • 0 in reply to Amrit Jit
    Intellectual 360 points

    Hello Amrit,

    these are unfortunately high Ron and pricey. 

    if I cannot find an electronic solution, I will revert back to using a physical switch to switch between the sources while having TPS22990 as a power on\off controller device per regulator.

    my output pins are ground, ground, 3.3v\5v, 5v. thus i need 5v fixed buck regulator, and for 3.3v\5v rail i had the idea of either having a fixed 3.3v buck to be switched by a physical or electronic switch with the same fixed 5v regulator.

    while another solution i had in mind is to use a buck regulator which is changeable from either 3.3v or 5v via changing feedback resistor and deliver the output to 3.3v\5v pin.

    I am afraid that when using 5v by the end-user, the 3.3\5v and 5v pins will be shorted together at target device which means the feedback of the 2 buck regulators will be the same. I believe this will create an issue.

  • 0 in reply to Hossam Moghrabi
    TI__Mastermind 31561 points

    Hello Hossam,

    I understand your concern.

    You can reach out to respective buck regulator query on e2e. Our respective engineers will help you.

    Thanks 

    Amrit