I am interested in using a LDO linear regulator, e.g. the On Semi NCP5501DT50RKG, to step down a voltage from 6-9 V to 5 V. It specifies that it is stable with output capacitors between 1 and 10 μF with an ESR of less than 4 Ω: LDO ESR stability

However, I'm intending on using it to power an IC which suggests the use of a >47 μF bypass capacitor.

With a low-ESR ceramic capacitor (perhaps 2.2 μF) at the output of the regulator, would the addition of a high-ESR electrolytic bypass capacitor cause any instabilities? Is this answer true in general for all LDO regulators which are stable with low-ESR output capacitors?

  • \$\begingroup\$ Wouldn't a high ESR defeat the purpose of a bypass cap? \$\endgroup\$ – marcelm Mar 23 '16 at 19:21

No it won't destabilize it, the low ESR capacitor will deal with the frequency range of concern for regulator stability. That should be true of any regulator that is stable with extremely low ESR (eg. ceramic capacitors).

You should place the low ESR cap close to the regulator.


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