Line driver with current source output and high immunity to rf signals

Abstract

Line driver for a LIN-bus. The line driver has a current source output transistor (T) for pulling down the LIN-bus wire (LB) to ground (GND). The LIN-bus wire (LB) is connected to a positive supply voltage (VBAT) through a pull-up resistor (R). The output transistor (T) is driven by a driver stage (DRV) in response to an input current (J) at an input node (X). The driver stage has a further resistor (R) connected between the gate of the output transistor (T) and a reference terminal (GND), a reference transistor (T) which has its source connected to the reference terminal (GND) and its drain coupled to the input node (X); the gates of the output transistor (T) and the reference transistor (T) are connected to an output (DAO) of a differential amplifier (DA) which has an inverting input (DAN) coupled to a bias voltage source (E) and a non-inverting input (DAP) coupled to the input node (X). The further resistor (R) stage provides a low-impedance path to ground for RF disturbances reaching the gate of the output transistor (T) through the drain-gate capacitance of the output transistor (T) and prevents these disturbances from penetrating the driver stage.