Dear TI team,
I have a question about the formulas shown in the figure. When applying these formula I seem to encounter a problem (picture and formula: https://www.ti.com/lit/an/slyt477/slyt477.pdf page 12).
For C1:
C1 = 1/(100*10^3 * 2Pi)^2 * 14.3*10^-6 = 1.77*10^-7 F = 17.7uF
This seems like a logical capacitance value, however when doing the same for C2:
C2 = 1/(((1*10^6 * 2Pi)^2) * (14.3*10^-6 - (1/(1.77 *10 ^-6))) = -4.5*10^-19 F
This seems far fetched. After doing multiple calculations with SI units and non SI units and different placements of brackets I eventually found a couple of answers which seemed more logical.
One of which is 1.8nF, this is currently on the design and it work together with the 17.7uF this allows Qi charging with a good efficiency (770mA expected, actual is 730mA).
However, the question remains: What am I missing in these formula, because I cannot seem to get the proper answer from it?
With kind regard,
Taner Aydin