AN3213 Datasheet, PDF (48/64 Pages) STMicroelectronics – ST7570 S-FSK power line networking system-on-chip

ST7570 demonstration board description
AN3213
Figure 44. Common mode disturbance protection - negative disturbance
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Figure 45. Differential mode disturbances protection
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Power supply
The power supply requirements for the ST7570 demonstration board are listed in Table 1.
However, the power supply circuit design is not only relevant in terms of available power.
Two points are particularly sensitive for a power line communication application:
● The noise injected on the line
● The input impedance of the power supply unit
For the first point, a quasi-resonant switching mode power supply based on the ALTAIR04-
900 device has been chosen. This kind of switching controller spreads the switching
disturbances over a wide frequency range, therefore minimizing the overall disturbance
amplitude.
The second point involves the EMI input filter design. The suggested circuit in Figure 46 has
been designed to have minimum influence on the ST7570 line coupling circuit, in terms of
load impedance and linearity. It is required to have a symmetrical circuit with two series
inductors to minimize differential noise and avoid capacitive load from the X2 capacitor.
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