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Original question:

About output capacitor (CL)and ripple noise of REF5025 & REF5050.

REF5030: ESR of output capacitor, stability

Patrick Ruf
Genius 4770 points
Part Number: REF5030

Hi,

I have the following questions concerning the output capacitor for REF5030. I want to make shure I understand the datasheet  (sbos410h, page 21) the right way (language issue).

a) I want to use a ceramic capacitor (10uF) that normally has a very low ESR in the range of 0.015 Ohm. Is the output of the REF5030 stable without a discrete series resistor?

b) If the answer to question a) is "yes", is it better to insert a discrete series resistor (of let's say 1Ohm) to improve noise performance?


Thanks and best regards,

Patrick

  • 0
    TI__Mastermind 19370 points

    Hi Patrick,

    I would follow the instructions from 9.4.1. and not the ones in the layout. I will change the layout instructions to make it consistent with the rest of the datasheet.
    a) The voltage reference should be stable because the ESR is less than or equal to 1.5 Ohms.
    b) The closer the ESR is to 1-1.5Ohms the better the noise performance of the REF50xx will be. Another options to improve noise performance is to add an additional capacitor on the TRIM/NR pin.

    You can use the following TI Design as an example. In this example they use a 1.24 Ohm resistor.
    www.ti.com/.../TIDA-00548

    I hope this answers your questions.

    -Marcoo Z