Grounding and AC Applications

AC line-powered applications that are not referenced to the ground can present a voltage potential difference to a debugger, emulator, or programmer referenced to earth ground or PC return through the USB connector interface of a PC. This can cause damage to both systems.

warning-clear-44.png WARNING
HighVoltage_Warning_84.png Electric Shock Hazard
Using the development tool without ensuring ground isolation will result in damage
to the tool or the target system as the full AC mains voltage will be applied.
This condition can be hazardous to the operator in the form of an electric shock.
Therefore, take adequate precautions to avoid this situation.


In these instances, the development tool must be isolated. Carefully consider the ground system and signal return connections before connecting the tool to the target. For hot or floating applications, a USB self-powered isolated hub should be used between the PC and the tool to provide isolation from the PC through the USB cable (see Figure 1).

USB isolated hubs such as the following are suggestions:

  • High/Low-Speed 4-port USB HUB, Model UISOHUB 4, B&B Electronics Mfg. Co.
  • High-Speed, 7-port USB HUB, Model HUB7i, SEALEVEL Systems, Inc.
  • Keterex Inc., Single USB port, Model P/N KXUSB-150.
  • IFTOOLS Gbr, Single USB port, Model ISOUSB-HVC.
non_isolated_ac.jpg
Figure 1: Example Debugger Setup for Non-isolated AC Power Systems
warning-clear-44.png WARNING
HighVoltage_Warning_84.png Electric Shock Hazard
Using an optoisolated USB hub will create a hot area (marked with the dotted red line in Figure 1 above). This condition can be hazardous to the operator in the form of an electric shock. Therefore, take adequate precautions to avoid this situation.

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