AN2744 Datasheet, PDF (22/56 Pages) STMicroelectronics – ST7538Q power line FSK transceiver

Board description
AN2744
Table 5.
Line coupling transformer specifications
Parameter
Turn Ratio
Magnetizing Inductance
Leakage Inductance
DC total resistance
DC saturation current
Interwinding capacitance
Withstanding Voltage
Value
1:1
> 1 mH
< 1 µH
< 0.5 Ω
> 2 mA
< 50 pF
4 kV
Figure 10 and Figure 11 show the measured response of the filter for both channels, loaded
with the CISPR reference network and with 5 Ω impedance. When loaded with the CISPR
network, the Tx passive filter gives an almost flat gain of nearly 3.5 dB around the
transmission carrier frequency. Applying a heavier load makes the frequency response
sharper and the gain at carrier frequency lower. This effect leads to a loss of about 7-8 dB
with a 5 Ω load for both channels.
Figure 10. Measured frequency response of the Tx passive filter for 72 kHz channel (typical)
10
5
0
-5
-10
-15
-20
-25
-30
-35
-40
1E+04
CISPR
5Ω load
1E+05
Freq (Hz)
1E+06
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