Low reflection driver for a high speed simultaneous bidirectional data bus
AssigneeInternational Business Machines Corporation
InventorKai D. Feng
Life of this patent
Estimating the term…
Abstract
A low reflection driver is provided for a high speed simultaneous bi-directional transmission line/data bus which is designed such that units at both ends of the transmission line/data bus can transmit data at any time without waiting for the bus to become available so that the baud rate of the bus is increased. A push-pull current source driver for the bi-directional simultaneous data bus provides greater flexibility for an output voltage swing, a matching impedance and bandwidth compensation.
Claims24
A simultaneous bi-directional data bus comprising:
- a simultaneous bi-directional data bus having a characteristic impedance Z0;
- a first driver unit and receiver unit connected to a first terminal end of the simultaneous bi-directional data bus;
- a second driver unit and receiver unit connected to a second terminal end of the simultaneous bi-directional data bus;
- each of the first driver unit and the second driver unit having a sourcing current source and a first resistor connected in parallel between a voltage supply and a terminal end of the simultaneous bi-directional data bus, and a sinking current source and a second resistor connected in parallel between a ground and a terminal end of the simultaneous bi-directional data bus, wherein a substantially higher impedance of each current source relative to a substantially lower impedance of each resistor connected in parallel to the current source provides a relatively constant impedance in each driver unit which substantially matches the characteristic impedance of the simultaneous bi-directional data bus.
A printed circuit board (PCB) communicating over a simultaneous bi-directional data bus having a characteristic impedance Z0, the PCB having a first driver unit and receiver unit connected to a first terminal end of the simultaneous bi-directional data bus, the driver unit having a sourcing current source and a first resistor connected in parallel between a voltage supply and the first terminal end of the simultaneous bi-directional data bus, and a sinking current source and a second resistor connected in parallel between a ground and the first terminal end of the simultaneous bi-directional data bus, wherein a substantially higher impedance of each current source relative to a substantially lower impedance of each resistor connected in parallel to the current source provides a relatively constant impedance in the first driver unit which substantially matches the characteristic impedance of the simultaneous bi-directional data bus.
A method of transmitting simultaneous bi-directional data over a bus comprising:
- providing a simultaneous bi-directional data bus having a characteristic impedance Z0;
- connecting a first driver unit and receiver unit to a first terminal end of the simultaneous bi-directional data bus;
- connecting a second driver unit and receiver unit to a second terminal end of the simultaneous bi-directional data bus;
- substantially matching the characteristic impedance of each of the first driver unit and the second driver unit to the simultaneous bi-directional data bus by providing each of the first driver unit and the second driver unit with a sourcing current source and a first resistor connected in parallel between a voltage supply and a terminal end of the simultaneous bi-directional data bus, and a sinking current source and a second resistor connected in parallel between a ground and a terminal end of the simultaneous bi-directional data bus, wherein a substantially higher impedance of each current source relative to a substantially lower impedance of each resistor connected in parallel to the current source provides a relatively constant impedance in each driver unit which substantially matches the characteristic impedance of the simultaneous bi-directional data bus.
Dependencies are inferred from the claim text.