Output noise – Atec Superior-Electric-L116b User Manual

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OUTPUT NOISE

Noise is specified in two ways: Spot Noise or Output Noise Density is the RMS sum of all noise sources, measured at the regulator
output, at a specific frequency (measured with a 1Hz bandwidth). This type of noise is usually plotted on a curve as a function of
frequency. Total Output Noise or Broad-Band Noise is the RMS sum of spot noise over a specified bandwidth, usually several
decades of frequencies.
Attention should be paid to the units of measurement. Spot noise is measured in units µV/root-Hz or nV/root-Hz and total output
noise is measured in µV(rms)
The primary source of noise in low-dropout regulators is the internal reference. Noise can be reduced in two ways: by increasing
the transistor area or by increasing the current drawn by the internal reference. Increasing the area will decrease the chance of
fitting the die into a smaller package. Increasing the current drawn by the internal reference increases the total supply current
(ground pin current).

LP38690
LP38692