US Patent 7948275 Transceiver with fault tolerant driver

A fault tolerant driver circuit includes a data output driver that receives an enable input and that includes a transistor formed on an isolation well. A well bias circuit provides a first well bias to the isolation well. The well bias circuit includes voltage-controlled impedances that are controlled by a voltage of the data output line, the enable input and a supply voltage. The voltage-controlled impedances connect the first well bias alternatively to: a common conductor through a first impedance when the supply voltage is ON and the enable input is ON; and a second impedance when the supply voltage is on and enable is OFF.