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What is the source of noise in an LDO regulator?

April 26, 2017LDO noise regulator source

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What is the source of noise in an LDO regulator?

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The LDO”s internal bandgap voltage reference is the source of noise, usually specified as microvolts rms over a specific bandwidth, such as 30 µVrms from 1 to 100 kHz. This low-level noise causes much less of a problem than the switching transients and harmonics from a switch-mode converter. In the figure below, the LDO has a voltage-reference bypass pin to filter noise using a capacitor to ground. Adding the datasheet-specified input, output, and bypass capacitors usually results in a non-problematic noise level.