Post Go back to editing

AD5141 in feedback loop of buck regulator

Hello,

We intend to use a AD5141 in the feedback loop of a buck regulator, for example as RFB2 with an ADP2300. Can this be considered a 'common use' of the AD5141 or do we have to expect problems compared to using a standard resistor?

many thanks and kind regards, Felix

  • This question is relevant to the AD5141, so I moved it to the Precision DAC community.

    DaveC

  • Hi Felix,

    Happy New Year!

    Yes you can use the AD5141 as a feedback resistor in a regulator.

    But there are few things to consider before using in this application.

    1. The output voltage of the regulator should be less than the maximum allowable voltage at the terminal of the digipot. In this case if the output voltage is 28V in the regulator, AD5141 cannot be used as the maximum voltage at the terminal is +7V.
    2. The current flowing through the Digipot should be less than the maximum allowable limit mentioned in the datasheet.
    3. Consider the the resistor tolerance which will affect the accuracy of the output of the regulator. Also, consider the wiper Capacitance which might impact the stability of the output of the regulator. 

    Regards,

    Koushik

  • Hello Koushik,

    Many thanks for your response. However I don't understand what you mean by point 1.

    In my ADP2300 example I suggested to use the digipot as RFB2 replacement. Since the voltage across RFB2 is typically 0.8V I don't understand what you mean by

    The output voltage of the regulator should be less than the maximum allowable voltage at the terminal of the digipot. In this case if the output voltage is 28V in the regulator, AD5141 cannot be used as the maximum voltage at the terminal is+7V

    Or was this just a general comment without relation to my example? Points 2. and 3. are clear.

    regards, Felix

  • Hello Koushik,

    Many thanks for the clarification and sorry, I forgot yesterday: Happy New Year to you too ;-)

    regards Felix

  • Hi Felix,

    In your case, where you are using it as replacement for RFB2 Resistor it will work fine since the typical voltage is is around 0.8V. 

    In General, make sure that the voltage at terminal A,B,W is less than or equal that off VDD of the digipot, as specified in the datasheet.

    Regards,

    Koushik