ST ST7540, Примечание к применению

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AN2451 Board description
Doc ID 12791 Rev 3 33/55
The possible environments for this kind of application can be both indoor and outdoor:
residential, commercial and light-industrial locations. To verify the immunity of the system to
environmental electrical phenomena, a series of immunity specification standards and tests
must be applied to the powerline application.
The requirements for ac-connected ports, fixed by the EN50065-2-3 document (part 7-
immunity specifications), include EN610000-4-4 (electric fast transients), EN610000-4-5
(surges), EN610000-4-6 (RF out-of-band disturbances), EN610000-4-11 (voltage dips).
In particular, surge tests are specified as both common and differential modes at level +/- 4
kV, with pulse shape 1.2 x 50 µs. Fast transient burst tests are specified at level +/- 2 kV, with
pulse shape 5 x 50 ns and pulse frequency 5 kHz.
Figure 29 , Figure 30 and Figure 31 illustrate the protection criteria implemented in the
ST7540 reference design.
Figure 29 and Figure 30 show the protection against common mode disturbances. The
BAT54S diodes are intended to prevent the voltage on PA_OUT and Rx_IN lines from going
above the supply rail (Vcc for PA_OUT and VDC for Rx_IN) or below ground, with a
tolerance equal to the forward voltage of the diodes, that is nearly 0.3 V.
Figure 31 describes the protection intervention in case of differential mode disturbances. A
differential voltage higher than 12 V is shorted by the bidirectional power transil, which is the
most robust protection and also the one capable to absorb most of the energy of incoming
disturbances.
Figure 29. Common mode disturbances protection - positive disturbance