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Galvanic isolation for USB devices

USB Isolators protect from faults and destruction

Along with Ethernet and WLAN, USB is among the most widely used communication interfaces. Even in industrial PCs the traditional COM ports (RS232/422/485) have largely disappeared in favor of multiple USB interfaces.

Ethernet network access points are by default equipped with at least 1kV of galvanic isolation to provide safe communication paths from an electrical point of view. USB on the other hand almost always creates a direct conducting interface between USB host (PC) and USB terminal device.

In industry an elsewhere this creates various problems for which USB isolators provide protection. The USB isolator is simply inserted into the existing USB connection.

How a USB isolator works

Protection for PCs and terminal devices

In the worst case a direct conducting connection caused by overvoltage or potential differences and the resulting compensation currents can lead to hardware damage. Various scenarios can be triggers for such problems:

Lightning strikes

The most extreme occurrence of overvoltage is a lightning strike. When it’s a direct strike - here we have to be honest - no isolator is going to help. But the situation is different when the strike is simply in the vicinity of electronic devices. A voltage funnel field forms around the point of impact and causes considerable potential differences, even if terminal devices are only a few meters apart.

USB isolator helps with lightning strikes

USB isolators can block up to 4kV depending on the model for effective hardware protection.

Defective 230V supply voltage

In industry you often find machines operating at high startup currents. Temporary potential shifts can occur in the event of poor or faulty supply networks, resulting in equalizing currents via the USB connection and thus destruction of the USB drivers.

Potential difference at contact resistors, USB isolator protects the hardware

USB isolators suppress the current flow across data lines, so that the hardware is protected.

Defective devices

Short circuits with live parts or other defects can result in external voltage being fed to the data lines.

USB isolator protects against external voltage

A USB isolator prevents external voltages from entering the PC.

Protection against malfunctions and data loss

Even if the previously noted problems do not cause direct hardware damage, they can compromise data transmission and even result in loss of data. There are additional scenarios having a negative effect on USB applications:

Ground loops

Signal ground and supply ground are often connected to each other in the terminal devices. In this case, the USB host and USB device have a ground connection via the power supply. The additional signal ground then results in a loop, which often causes mains hum. This can be very challenging in USB audio applications. But ground applications or sensors connected via USB may also provide falsified values

USB isolator interrupts ground loop

A USB isolator interrupts ground loops and thus reduces or eliminates problems caused by mains hum.

Antenna effects

Systems with a direct ground connection are more sensitive to interference. In industrial environments in particular, you often have to deal with a noisy electrical environment. Interference pulses captured in this way on the USB data lines can falsify the transmitted data. Depending on the USB operating mode, incorrectly received data will be repeated - but this slows down the data rate. USB isolators offer protection here as well.

Protection for life and limb

Wherever persons could come into contact with a USB terminal device, it should be ensured that no hazardous voltages are present at the USB terminal device, for example due to a defect in the PC. This is particularly true in the medical sector, but also wherever there the public is present. Here too, USB isolators ensure clean separation.

Bridging distances

The maximum cable length for standard USB connections is 3m to 5m, depending on the USB standard used. USB isolators do not increase the maximum distance, buit do provide added data security.

If greater distances are required, we recommend the use of a USB server. The USB server remotes the actual USB connection to any location in the network - in most cases even across networks. Galvanic isolation of the network connection also offers all the advantages of a USB isolator.


  • #33001

    USB Isolator 1kV
    USB Isolator 1kV

    Cable versions for inserting

  • #33003

    New USB Isolator 2kV HS
    USB Isolator 2kV Hi-Speed

    Cable version for all USB 2.0 devices

  • #33204

    USB Isolator 4kV
    USB Isolator 4kV

    USB-powered isolator with high isolation voltage

Additional information

Could you use some assistance?

Should you have questions or need assistance with these products, you are welcome to contact me.

Employee photo - Thiel
Frank Thiel