Bus driver circuit with overvoltage protection

摘要

A bus driver circuit having a driver input (16) for the reception of a data signal and a driver output (20) for the application of the output voltage of a voltage source (Vcc) to a bus core (10) in a manner dependent on the presence of a data signal at the driver input (16). It possesses a first controllable switch (A) placed between the voltage source (Vcc) and the driver output (20) and a control circuit loop (B), which on the application of the data signal to the driver input (16) is able to be placed in an active state by its producing a drive signal putting the controllable switch (A) in a conducting state. A second controllable switch (C) is between the control circuit loop (B) and the driver input (16). A comparator (D) compares the voltage at the driver output (20) with a reference voltage (Vref) and when the voltage at the driver output (20) exceeds the output voltage (Vcc) of the source, provides a control signal which turns off the second controllable switch (C) and puts the control switch loop (B) in the inactive state by turning off the first controllable switch (A).