ESR vs DF calculations

[interjaz]

Hello,

Recently I was looking for low ESR capacitor, for PIC18F46J50.
I looked over some datasheets and I got little bit confused when I found DF and ESR values.
I tried to get answer on other forum too, but without any result yet.

As we know basic equitation is

DF = ESR / Xc

So I found SMT tantal AVX caps **broken link removed**
Especially I am interested in TPSB106*016#0800 10uF

Quote from datasheet:

All technical data relates to an ambient temperature of +25°C.
Capacitance and DF are measured at 120Hz, 0.5V RMS with
a maximum DC bias of 2.2 volts. DCL is measured at rated
voltage after 5 minutes.

So I wanted to calculate ESR for 120 Hz.

Xc = 1/(2 * PI * f * C)
ESR = DF * Xc
ESR = 8

ESR = 8 Ohms it is quite a lot. So I wanted to verify that data with SpiTanIII software provided for tantal caps form AVX.





As you can see there some differences.
DF = 6% (60m) is rather on 1.5kHz then on 120Hz, 8 ohms in such range is impossible to get.

My questions is: why there are such differences? Didn’t I understand the theory right or just misinterpret the information form datasheet.

Any response would be helpful,
Thank you very much!