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What defines "LOW ESR"?

Former Member

A parts list calls for LOW ESR capacitors (in the TL499A switchmode controller PSU).

 

It has been suggested that 105 degC capacitors could be substituted, but I figure I should also choose those that start off in the ball-park.

 

So what actually defines "LOW" in "LOW ESR"?

 

[UPDATE] The attached is the data sheet for the recommended parts

Attachments:
imageTS13DI-CD286.pdf
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    A wrapped capacitor has inductance and resistance. Low ESR capacitors are made by making multiple connections to the foil.
    The ESR will cause the capacitor to become hot as a result of the ohmic losses and high charge and discharge currents.
    Low ESR can be defined in two ways. It is possible to define a resistance value for the ESR. This however is frequency dependant. The other way is to define the impedance at a certain frequency, as has been done in the datasheet of the recommended capacitor.
    With the formula Xc = 1: 2*pi*F*C  you can calculate the theoretical impedance of the capacitor.
    The difference between the theoretical impedance and the real value is caused by the ESR.
    So you can calculate the value of the ESR. At higher frequencies the theoretical impedance of the capacitor can be neglected and the given impedance at a certain frequency can be used as ESR for calculating the losses.