LINE RECEIVER CIRCUIT WITH ACTIVE TERMINATION

摘要

A circuit for receiving digital signals over a transmission line. A feedback circuit is coupled to an input node of the transmission line and adjusts the input impedance of the receiver circuit to match the characteristic impedance of the transmission line. The feedback circuit includes a first current source controlled by a first voltage and having a first transconductance, and a second current source controlled by the first voltage and having a second transconductance equal to the first transconductance times a first scaling factor. The feedback circuit includes a first resistance element having a resistance equal to the first scaling factor plus one, times the characteristic impedance of the transmission line, and is coupled between the outputs of the first and second current sources. Finally, the feedback circuit also includes a differential amplifier that compares the output of the first current source to a reference value then generates the first voltage output to control each of the first and second current sources.

主权项

1. A circuit for receiving digital signals, comprising:
a first input node configured for connection to a transmission line having a characteristic impedance; a second input node configured for connection to a common line for the transmission line; a first current source controlled by a first voltage and having an output coupled to a first internal node, the first current source having a first transconductance; a second current source controlled by the first voltage and having an output coupled to the first input node, the second current source having a second transconductance equal to the first transconductance times a first scaling factor; a first resistance element coupled between the first input node and the first internal node, the first resistance element having a resistance equal to the scaling factor plus one, times the characteristic impedance of the transmission line; and a first differential amplifier having a first input coupled to the first internal node and a second input configured for receiving a first reference voltage with respect to the second input node, the first differential amplifier generating the first voltage as an output to control each of the first and second current sources.