Board description
AN2451
20/55
Doc ID 12791 Rev 3
Figure 10.
Measured frequency response of the Tx active filter (typical curve)
Simulation of the Tx active filter response against components' tolerance, depicted in
, shows +/- 1 dB variation in gain module at 72 kHz.
Figure 11.
Simulated frequency response of the Tx active filter with components
tolerance effect
5.1.2
Tx passive filter
Coupling to the power line requires some passive components in addition to the active
filtering stage. In particular, Tx passive filter section is made of the decoupling capacitor
C22, line transformer T2, inductor L5 and X2 safety capacitor C23.
L5 has been accurately chosen to have a high saturation current (>1 A) and a very low
equivalent series resistance (<0.2
Ω
), to limit distortion and insertion losses even with heavy
line load. Center frequency for the series resonance is calculated as:
Equation 3
+/
‐
1
dB
f
c
1
2
π
L
5
C
23
•
---------------------------------
=
