Termination circuit for network interface unit
AssigneeAdtran, Inc.
InventorDavid E. Jones
Life of this patent
Estimating the term…
Abstract
A network interface unit has an interface coupled to a first transmit line and a first receive line, and the interface is configured to receive a signal from the first receive line. The network interface unit further has circuitry operable in a test mode and a data mode that couples the received signal to the second transmit line via a first path while operating in the data mode. The circuitry further disables coupling of the signal to the second transmit line, couples the signal via an alternate path to the first transmit line, and creates a bias voltage about which a termination impedance for the second transmit line is centered while operating in test mode.
Claims18
A network interface unit, comprising:
- an interface coupled to a first transmit line and a first receive line, the interface configured to receive a signal from the first receive line;
- a transformer coupled to the interface and a second transmit line;
- circuitry operable in a test mode and a data mode, the circuitry configured to couple the received signal to the second transmit line via a first path through the transformer while operating in the data mode, the circuitry further configured to disable coupling of the signal to the second transmit line and couple the signal via an alternate path to the first transmit line in the test mode;
- and
- at least one resistive element coupled to the transformer and the interface and within the first path such that the signal passes through the at least one resistive element between the transformer and the interface in the data mode,
- wherein the circuitry is further configured to quietly terminate the second transmit line in the test mode by coupling the at least one resistive element to a return path such that noise on the second transmit line is absorbed by the at least one resistive element in the test mode.
A method for terminating a communication line, the method comprising the steps of:
- receiving a signal from a first receive line;
- coupling the received signal through at least one resistive element and a transformer to a first transmit line via a first path while operating in a data mode;
- disabling the coupling of the received signal through the at least one resistive element and the transformer to the first transmit line step while operating in a test mode;
- coupling the signal via an alternate path to a second transmit line in the test mode;
- and
- quietly terminating the first transmit line in the test mode, the quietly terminating step comprising the step of coupling the at least one resistive element to a return path such that noise on the first transmit line is absorbed by the at least one resistive element in the test mode.
A quiet termination circuit, the circuit comprising:
- a transformer coupled to a transmit line;
- a first transistor coupled to a second transistor, the first transistor and second transistor further coupled to the transmit line, the first transistor and the second transistor configured to remain inactive while data is transmitted via the transmit line in a data mode;
- at least one resistive element coupled to the transformer and the transistors, the data transmitted through the at least one resistive element during the data mode;
- and
- control logic configured to activate at least one of the first or second transistors in test mode in a test mode such that noise on the transmit line is absorbed by the at least one resistive element thereby quietly terminating the transmit line in the test mode.
Dependencies are inferred from the claim text.