From the datasheetdatasheet, there is no risk to the TP-UART
if you power through the USB when there's no external power (I assume KNX
is P1
). Relevant information is below Table 4in Section 1.1.1:
Entries c
and d
, tellThis tells you that there is no damage if \$V_\mathrm{VCC} > V_\mathrm{VSP}\$ and when \$V_\mathrm{IF} \geq V_\mathrm{VCC}\$ respectively. These are the conditions that would be met if you were using \$V_\mathrm{USB}\$ to power the device.