On the STM32 Nucleo-144 eval board, there are 3 different ESD protection devices for the USB port:
U19 = USBLC6-2SC6
U21 = ESDA7P60-1U1M
U22 = ESDALC6V1-1U2
Can anyone give information on why these are chosen, especially, why there are two different types chosen for the VBUS (voltage supply) and the ID signal protection? How necessary is it to have this exact types?