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REF6225: REF6225 Reference Voltage

Carlos Martins81
Intellectual 450 points
Part Number: REF6225
Other Parts Discussed in Thread: REF6025

Hello,

At this time, I'am work with a REF6225 voltage reference. Through the analysis of the data sheet, I'am saw that it would be necessary to use a capacitor with a series resistor at the output of the REF6225.
In this way, some doubts arose:
What type of capacitor (tantalum or ceramic) makes the circuit more efficient?
If I use tantalum capacitor, the value of the ESR resistor is not the same as the ESR value of the tantalum capacitor?

I attach the schematic of my circuit.

Thank you.

  • 0
    TI__Mastermind 19370 points
    Hi Carlos,

    It is not necessary to add an additional ESR Resistor if the capacitor ESR is sufficient.
    Ceramic capacitors are ideal because of their low ESR which allows the flexibility to add an additional ESR resistor if you need it to meet the DS recommendations.
    Example of schematic with the REF6225 can be seen in the REF6025 EVM.
    For efficiency, I do not believe tantalum vs ceramic would make a significant difference. I would still use ceramic and adjust the ESR with an external resistor.

    -Marcoo Z
  • 0
    Guru 140200 points

    Hi Carlos,

    figure 52 of datasheet shows, that for the REF6225 the ESR of output cap should be between 20mR and 100mR. For a tantal it's difficult to ensure this, because the ESR of tantal significantly varies with temperature. More, the actual ESR differs from manufacturer to manufacturer and shows production tolerances. Because of that, ceramics are a welcome alternative. Their ESR is very low and does not vary much with temperature. So, the simpest way to choose a suited output capacitor would be to take a ceramic cap and add a series resistor to provide the needed ESR for stability.

    Kai

  • 0 in reply to kai klaas69
    Intellectual 450 points

    Hello Kai,

    Thank you for your suggestion.

    Thus, to make my circuit more efficient I can place a ceramic capacitor of 47uF in series with a resistance of 50 mΩ to stabilize the value of ESR.

    Am I right?

    Thank you very much.

  • 0 in reply to Carlos Martins81
    Guru 140200 points
    Hi Carlos,

    yes, you are right!

    Kai