What isolation requirement should LAN transformer or ICM RJ45 to be followed ?LAN transformer follow IEEE 802.3 Isolation requirement.
How to layout the Center Tap of LAN transformer or ICM RJ45 on PCBA ?It's depend on the driving type of your LAN Chip, the suggestion are as below:
Is it suitable to pull high LED 3.3V power with 330 ohm resistance ?This resistance called "Current limiting resistor", the function is to adjust the light intensity of LED, please to keep the Forward Current below the limit value in case to burn out the LED. The formula of Current is as below:
I=V/R=(V power - Vf)/Current limiting resistor