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Original question:

REF3030: Need more information as references

REF3030: REF3030

Paulo Pecegueiro
Prodigy 120 points
Part Number: REF3030
Other Parts Discussed in Thread: REF102
Hi,
I would like to take some doubts about the current capacity of the REF3030. 
In my application I have 6 loads of 350 ohms that will be powered by 3V, so the total drained current will be almost 52mA. 
I know that the maximum output current of the REF3030 is 25 mA and the voltage drop will be 300mV, I also know that the REF3030 has a buffer inside its output to provide the maximum current of 25mA. 
Having seen all these points, I would like to know if there is any problem in putting 3 REF3030 in parallel to supply the 52mA I need. 
I could supply 2 loads in each REF3030, but my intention is to create a unique 3V power plane.
Thank you everyone attention!
  • 0
    TI__Mastermind 19370 points

    Hi Paulo,

    I would not recommend to run 3 REF3030 in parallel. If you need more output current we do have alternatives.

    For example, look at figure 7 of the REF102 datasheet for output current boost capabilities. I will recommend to use figure 7b with the REF3030 as this can give a much higher and safer output current

  • 0 in reply to Marcoo Z
    Prodigy 120 points

    Hi, thanks for your reply. I thought I could use a transistor to improve the current, but I was afraid to introduce noise or even lose the accuracy of the reference voltage. Could you guide me in selecting a transistor?

  • 0 in reply to Paulo Pecegueiro
    TI__Mastermind 19370 points

    Hi Paulo,

    I think I might be confused sorry. Are the outputs of the REF3030 connected to each other? If you just need 3 REF3030 that are connected separately to 2 350Ohm loads then there should be no issues. I just do not want to connect the outputs of the REF3030 together

  • 0 in reply to Marcoo Z
    Prodigy 120 points 
    I was using a single ref3030 to power 2 loads, I have no problem with that.
    But to optimize the layout and generate a single power plane, I need a 3V power supply with a very low noise level and a current capacity of more than 52mA.
    Then I had the idea of ​​putting three of them in parallel (max current of 75mA), since their output has buffers, I thought there would be no problems.
You informed me that it is not recommended and presented the idea of ​​using a transistor to amplify the output current, I would like to know what I can expect when making this adaptation. 
    What would be the changes in the output ripple, noise and etc?
    Thank you.
  • 0 in reply to Marcoo Z
    Prodigy 120 points

    Hey Marcoo, could you reply me?

    "I was using a single ref3030 to power 2 loads, I have no problem with that.

    But to optimize the layout and generate a single power plane, I need a 3V power supply with a very low noise level and a current capacity of more than 52mA.
    Then I had the idea of ​​putting three of them in parallel (max current of 75mA), since their output has buffers, I thought there would be no problems. You informed me that it is not recommended and presented the idea of ​​using a transistor to amplify the output current, I would like to know what I can expect when making this adaptation.
    What would be the changes in the output ripple, noise and etc?
    Thank you."

    This is what I am planning to use:

  • 0 in reply to Paulo Pecegueiro
    TI__Mastermind 19370 points

    HI Paulo,

    There is one big issue with this design and that the 3.3V rail will not cause enough of a voltage difference to supply the 0.7 VBE. Do you have a higher voltage rail?

  • 0 in reply to Marcoo Z
    Prodigy 120 points

    Oh, My mistake. Yes I have 4.5V voltage rail.

    I would like to know what I can expect when making this adaptation.
    What would be the changes in the ripple and the noise in the 3V rail output?

  • 0 in reply to Paulo Pecegueiro
    TI__Mastermind 19370 points

    The REF30 has a AB output stage so it can adapt and make sure the output is regulated on overshoots and undershoots. The performance will be limited to an extent because it is dependent on how clean the 4.5V stage is. I do not expect the accuracy/temp drift to change. The main change will be related to the AC parameters so the power supply will hopefully be an LDO or another linear regulator.