LDO Noise SLYY076 Application Note

Hi Matthieu,

Wow, this is kinda embarrassing but looking at it I see that equation 6 is incorrect. You'd think that after reading and re-reading your own white paper so many times it would be free of such mistakes. Below is the equation that should have been in the paper (and I'll work on having it updated so it's correct). 

In order to "graphically integrate" the noise we are performing a midpoint Riemann sum (see the illustration bellow for an example). To determine the midpoint (vertically) we add the two noise measurements (which requires them to be squared individually since they are assumed to be uncorrelated and Gaussian) and then divide by 2. to get the area of the rectangle we then multiply by the width of the rectangle which is the change in frequency between the two measurements. We add all of these rectangles and then take the square root of that to get the RMS Noise.

Let me know if any of that isn't clear or if you have any other questions, and like I said I'll work on getting the white paper updated. 

-Kyle Van Renterghem

Hi Kyle,

Thanks a lot for your feedback.

It's almost clear right now. The only point not very clear is the explaination about why you have to square each measurements indivdually before to add it.

Is it to make like an average quadratic?

If you can detaileda little this part but perhaps, I have to take a glance on the midpoint Rienmann sum for this point.

Matthieu Baque

Hi Kyle,

Like I said, the only point that isn't very clear is the square. More than a quadratic average, Is it to have a power instead of voltage?

Could you just detailed this part or give me a link with an app note to explain that, plesae?

Many thanks

Matthieu Baque