what is the meaning of ESR of Cout in a LDO? thanks

stabilizing ldo

Dear all:
My question is what is the meaning of ESR of the output capacitor in a LDO?
and where dose the ESR come from?
could you help me? thank you very much!


Ken

esr means

ESR means Electrical Series Resistance of the load capacitor at LDO's output. Typically LDOs need the load capacitors to have low ESR.

To have more insight to ESR effect on LDO performance you might want to read the LDO book written by Rincon Mora (download from this link)




ESR of any device is described as:
ESR is the real resistive component of the complex impedance Z(w) = R + j X(w) of the device; this complex impedance can involve several relatively minor resistances, inductances and capacitances. These small deviations from the ideal behavior of the device can become significant when it is operating under certain conditions, i.e. high frequency, high current, or temperature extremes. Different ways have been developed to represent the non-ideal behavior of electrical components, ESR being just one of them and each tailored to the typical way a component is used.

Good luck.

Let me make a small correction to shirin_br's post. ESR stands for Effective Series Resistance or Equivalent Series Resistance.

thank you very much for all your help.

does it need add a small res series the load cap when running simulations?

yes, if you used ceramic cap , the ESR will be from 20mohm to 120mohm

ESR adds zero while doing compensation

You should specify the RES range in your design spec.

ESR helps you in stabilizing in LDO. It's value is improtant and yes, you should specify in your design

what will be the ESR of 3300 pF ,3 kV CERAMIC CAPACITOR

paley said:

yes, if you used ceramic cap , the ESR will be from 20mohm to 120mohm

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