Hello,
I am doing some tests to design an EMI input filter for LM5145.
I made a double check using two different tools, but I found different values of Irms for current sharing of input capacitors.
Here are the results with Power Stage Designer:
3.78A and 1.91A for C1 and C2 respectively.
But if I use the following Excel calculator:
e2e.ti.com/.../Worksheet-in-Switching-Power-Supply-Design_5F00_-EMI.xls
with Cd = 100uF and CIN = 22uF and same operative conditions, gives me these quite different results:
Looking at the used formulas, the Excel tool seems to have some errors:
1) Capacitor impedance module is calculated as a simple sum instead of a "square root of a sum of squares":
2) In the formula that calculate Irms in each capacitor, the square root of the ratio of impedances is missing:
After having modified the formulas, as indicated above, I have finally found a perfect match with Power Stage Designer:
Are there any reasons of these apparently wrong formulas in the Excel tool?
Thank you and regards,
Massimo
