Proper ESD/overvoltage protection for USB

[Unixon]

There are different components available for the purpose of protecting a USB device from ESD as well as the USB host from a malfunctioning USB device: special multiport TVS, small discrete TVS, power TVS, zener diodes, etc. As far as I've seen, different schematic solutions use different approaches depending on real availability of components.

Out of all combinations I found by experiment that power TVS doesn't work for data lines even if they safely pass on voltage rating, probably due to high capacitance.

What would you use for your project?

[VK3DRB]

I assume you are mainly interested to protecting the data lines. For the data lines, BAT54S are a cheap and common solution. Pin 3 on the data line, pin 1 to ground, pin 2 to +5V rail. Low capacitance, low turn on voltage and fast switching.

Depending upon what the USB is driving, use a TVS and capacitor across the rails at the device.

[T3sl4co1l]

BAT54 is way too much capacitance for USB if you're going to touch High Speed.  Schottky diodes with low enough capacitance don't handle enough peak current, so your only other option is junction diodes: usually small avalanche diodes, or clamp diodes into a somewhat bigger TVS (that usually doubles for VCC protection).

As for EMI/RFI protection, USB is simply completely the wrong standard for that kind of environment.  Use fully shielded connectors and cables everywhere possible, but don't expect miracles.

Tim

[tszaboo]

Most manufacturers - who make TVS protection- have some kind of selection guide. USB is usually a custom solution. IE TPD2E1B06

[VK3DRB]

BAT54 is way too much capacitance for USB if you're going to touch High Speed.  Schottky diodes with low enough capacitance don't handle enough peak current, so your only other option is junction diodes: usually small avalanche diodes, or clamp diodes into a somewhat bigger TVS (that usually doubles for VCC protection).

As for EMI/RFI protection, USB is simply completely the wrong standard for that kind of environment.  Use fully shielded connectors and cables everywhere possible, but don't expect miracles.

Tim

Yep, depends on the application, what USB type, and other things like the series resistance and other capacitances. BAT54S's go down to roughly 2pF at 5V_R. Some zeners go down to 0.3pF.

[RenGate]

Some manufacturers produce diode arrays with TVS in one package for as many data lines as you need. For my last project I decided to try MAX3207E IC http://www.maximintegrated.com/en/products/interface/protection-and-isolation/MAX3207E.html, which protects two data lines. There is also similar solution from ST, USBLC6-2SC6 http://www.st.com/web/en/resource/technical/document/datasheet/CD00050750.pdf. Overall, I think such ICs are a good choice for their small footprint size and price  .