ADM7150 increase output voltage

Is it possible to increase the ADM7150 output voltage to 12V using this kind of circuit?

will the output noise increased?

what is the max and min value of r1 and r2 can be used?

  • 0
    •  Analog Employees 
    on Jan 22, 2015 12:22 AM over 6 years ago

    If you really need low noise (<2uVrms or even <20uVrms) then the LM317 will not be able to achieve that.

    Most LM317 have noise levels of 50-100 times per volt or 1000x the noise if you are trying to generate 12V.

    Could you use the ADP7118 or ADP7142? This will have noise around 12uV at 12V output.

    See the DESIGN EXAMPLE OF USING THE NOISE REDUCTION NETWORK WITH THE ADP7142

    in the following app note:

    http://www.analog.com/static/imported-files/application_notes/AN-1329.pdf

    ADI's new LDOs have this ability to use fixed voltage LDOs, like a 5V preset version, and raise it's voltage above the set point instead of having to use the 1.2V version of the LDO to do that. Noise is improved by setting the reference voltage internally in addition to the noise reduction technique described in the app note.

    Luca

  • Theoretically you could do something like this, but your caps should go to ground.

    Yes, the noise will increase.  The R1/R2 have to draw the min load current required by

    the regulator, which is zero for the 7150.  If they are too low, all the current goes into

    the divider and you have nothing left for your load.

    Best to use an LM317 three terminal adjustable that was designed for this.

    Also see the three app notes.

    Harry


  • 0
    •  Analog Employees 
    on Aug 2, 2018 2:53 PM over 2 years ago
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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    EZ Admin