AN3213 datasheet(48/64 Pages) STMICROELECTRONICS

48 / 64 page

ST7570 demonstration board description

AN3213

48/64

Doc ID 17429 Rev 1

Figure 44.

Common mode disturbance protection - negative disturbance

Figure 45.

Differential mode disturbances protection

7.7

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.

AN3213 Datasheet(PDF) 48 Page - STMicroelectronics