EMI Bites: Your USB Cable Is an Antenna—Now What?
EMI Bites: Your USB Cable Is an Antenna—Now What?
Think about this:
A USB cable coming from the outside world plugs into your board.
It's meters long, and it’s more than a cable, It’s a perfect antenna for coupling external noise right into your circuit.
If you don’t protect the interface where that signal enters the board, your microcontroller is left exposed.
Why this causes problems:
- Long cables act as antennas, picking up noise from the environment.
- That noise travels down the cable and reaches your connectors.
- If there’s no protection, the noise goes straight into your internal circuitry.
- It only takes one pulse to disrupt or damage your system.
Key Insight:
Protect your inputs and outputs right at the boundary—don’t let noise into your system.
How to protect I/O lines like USB:
- Place TVS diodes or filter components immediately at the connector.
- Keep traces between the connector and protection components as short as possible.
- Apply the same strategy to all external I/Os—USB, Ethernet, CAN, GPIO, etc.
Hope this helps,
Dario
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