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LMZ10501 Parallel Output Toggling

Michael Hershkovich
Prodigy 230 points
Other Parts Discussed in Thread: LMZ10501

Hi,

I'm thinking of a generic power supply design in which I'm connecting two or more LMZ10501's outputs together and enabling only one of them using a controller. For example, if I need in the field to choose between 1.8v power supply or 3.3v power supply. According to the datasheet details I don't see any problem to do that, but someone can confirm that?

Thanks,

Michael

  • 0
    TI__Genius 15810 points

    Hello,

    You can have a controller enable either power supplies based on the need and that should not be a problem. You could even have them enabled at the same time, but you'd need to make sure that the input power supply that's feeding the two DC-DC regulators is strong enough to supply current when both are on. I hope this helps.

    Regards,
    Akshay

  • 0 in reply to Akshay Mehta
    Prodigy 230 points

    Hi Akshay,

    Are you sure?  Connecting 3.3v output  directly to 1.8v output when both Switchers are enabled will not do any harm?

    So, what if I'm connecting two modules of 3.3v, will I get current sharing of 2A ?

    I just want to make sure you understand my first question. I want to connect two or more Switchers together which

    each one of them generates different output voltages, and enabling only one of them according to the system demand,

    and kinda hopping that if I enables one of them the others will be at HI-Z output state. According to the Switcher's

    block diagram, as long as all the VINs for all the Switchers are the same, I don't see a problem. 

    Can you please confirm that again?

    Thanks,

    Michael

  • 0 in reply to Michael Hershkovich
    TI__Mastermind 19891 points

    Hello Michael, 

    I assume you want to have something like this:

    I have not tried this, but  it should should work as long as VIN is there.You cannot have both regulators enabled at the same time because they will fight each other. This condition should be avoided by the inverter at the EN pin of the 3.3V regulator above.

    Now, if you don't need more than 1A of output current, you can also achieve this with a single LMZ10501 module. You can change the output voltage on the fly by changing the voltage divider ratio from Vref to Vcon. You could try something like this:

    Regards, 
    Denislav

  • 0 in reply to Denislav Petkov
    Prodigy 230 points

    Hi Denislav,

    First of all thank you for your detailed answer!

    Second, What did you mean when you wrote  "if you don't need more than 1A of output current, you can also achieve this with a single LMZ10501 module", are you implying that if I use two modules with the same Vout it's possible to do current sharing with this module to get more than 1A ?

    Thanks,

    Michael

     

  • 0 in reply to Michael Hershkovich
    TI__Mastermind 19891 points

    Hi Michael, 

    You cannot do current sharing with this particular module (at least not without additional external circuitry). 1A is the maximum output current you can get. I suppose I was still thinking two separate outputs when I made that statement above and I see how it implied possible sharing...Sorry for the confusion. Even if you use your initial two modules approach, your maximum output current is still 1A. 

    I would suggest the second approach with the divider ratio change. It seems more cost efficient and will save you some space too. It should be fairly easy to try it on an evaluation board. Here is a link to the eval board page: http://www.ti.com/tool/lmz10501silevm

    Cheers, 

    Denislav

  • 0 in reply to Denislav Petkov
    Prodigy 230 points

    Hi Denislav,

    Thank you!

    Michael