Bus driver circuit with improved transition speed

摘要

A bus driver circuit comprising:a first and a second circuit node (CANL, CANH; BM, BP), the first circuit node (CANL; BM) being operatively coupled to a bus line (BUS) having a bus capacitance ( CBUS) between the first and second circuit nodes (CANL, CANH; BM, BP);a switching circuit (T1-T4) which is coupled to the first circuit node (CANL; BM) and is designed to apply an output voltage (VBUS) between to apply to the first and the second circuit node (CANL, CANH; BM, BP), whereby the bus capacitance (CBUS) is charged when a control signal (STX) indicates a dominant state;a discharge circuit comprising at least one resistor (Ro), wherein the discharge circuit is coupled between the first and the second circuit node (CANL, CANH; BM, BP) and is designed to allow the bus capacitance (CBUS) to be discharged via the resistor (Ro) when the control signal (STX) has a recessive show status wherein the switching circuit is further configured to provide, in addition to the discharge circuit, a temporary current path for discharging the bus capacitance (CBUS) during a transition time period from a dominant to a recessive state,wherein the switching circuit has at least one third transistor (T2). , which is connected to the first circuit node (CANL; BM) is coupled; the temporary current path is formed by the third transistor (T2), which is designed to be activated temporarily in accordance with the control signal (STX), the at least one third transistor (T2) being selected from a large number of transistor cells or groups of transistor cells (T2 ,1, T2,2, ..., T2,N, ..., T2,2N) having load current paths connected in parallel to form the load current path of the third transistor (T2) having an effective resistance;wherein the transistor cells or groups of transistor cells are adapted to be switched on or off sequentially, so that the effective resistance of the third transistor (T2) depends on the number of transistor cells, or groups of transistor cells, that are switched on.