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LP38798: Consult about Low Noise

WU YISYUAN
Expert 2165 points
Part Number: LP38798
Other Parts Discussed in Thread: LP2985

Hi,

     I have some question in low noise application.

     I want to use LP38798 drop volt to 12V, and use LP2985 drop 9V to OPA use.

     I see datasheet define LP38798's noise is 5uV, LP2985's noise=30uV.

     What is the noise output?
      Is the noise LP38798 5uV or LP2985 30uV?

thanks.

  • 0
    TI__Guru 55940 points
    Hi Wu,

    For linear regulators, the output noise is the self generated noise which comes primarily form the internal reference. PSRR is a measure of the regulators ability to filter the input rail. Since the ultimate goal is a "clean" output rail, you will want a regulator with a high PSRR metric and a low noise metric.

    In your application the LP38798 noise will be filtered by the PSRR of the LP2985; however, you will still see the self generated noise from the LP2985 on the output.

    Very Respectfully,
    Ryan