POWER-OFF PROTECTION CIRCUIT FOR AN LVDS DRIVER

A power-off protection circuit for an LVDS line-driver eliminates initialization problems in a local LVDS driver circuit that are caused by a remote LVDS driver when the local LVDS driver is disabled. The remote LVDS driver may introduce a signal into the substrate of the local LVDS driver when the local LVDS driver is in a power-off mode. A current source in the local LVDS driver couples power from a local power supply node to the local LVDS driver when power is active. A method and protection circuit connects the substrate of the current source to the local power supply when power is active, and decouples the substrate from the local power supply when power is deactivated. The remote LVDS driver cannot cause a false power supply signal in the local LVDS driver since the conduction path is disconnected. A first switching element couples a floating substrate node in the current source to the local power supply when the power is active. A second switching element couples the floating substrate node to a bias line when power is deactivated. The first switching element is deactivated by a rising potential in the floating substrate when the local power supply is in a power-off mode. The rising potential is caused by a signal that is transmitted by the remote LVDS driver. By isolating the floating substrate from the local power supply, false signals are eliminated and initialization problems are avoided.