Switch selectable terminator for differential and pseudo-differential signaling
First Claim
1. A termination network for configuring the termination of first and second adjacent transmission lines for either two data line pseudo-differential signaling or single data line true differential signaling comprising:
- first circuitry coupled to the first transmission line and configured in response to a first logic state of a first control signal to terminate the first transmission line in a first impedance referenced to a first bias voltage for pseudo-differential signaling;
second circuitry coupled to the second transmission line and configured in response to the first logic state of the first control signal to terminate the second transmission line in a second impedance referenced to a second bias voltage for pseudo-differential signaling; and
third circuitry for coupling the first circuitry to the second circuitry thus configuring the first and second circuitry as a third impedance termination between the first and second transmission lines in response to a second logic state of the first control signal for true differential signaling.
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Accused Products
Abstract
An active terminator is configured with switches to select between terminating two lines for transmitting one differential signal pair or two single ended signals terminated in a pseudo-differential receiver. The receiver circuitry is configured with three differential comparators. One differential comparator receives both signal lines and other two differential comparators each receive one signal line and a reference voltage. The signal lines are terminated in a resistive voltage divider with electronic switches coupling the positive and ground voltages. The top and bottom nodes of the resistor divider in both terminators are cross-coupled with pass gates. In the pseudo-differential mode the pass gates are OFF and the electronic switches are ON with known resistances. In the differential mode, the electronic switches are OFF and the pass gates are ON with known resistances. The pass gate and switch resistances are sized with the resistors to insure a desired termination impedance.
93 Citations
20 Claims
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1. A termination network for configuring the termination of first and second adjacent transmission lines for either two data line pseudo-differential signaling or single data line true differential signaling comprising:
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first circuitry coupled to the first transmission line and configured in response to a first logic state of a first control signal to terminate the first transmission line in a first impedance referenced to a first bias voltage for pseudo-differential signaling; second circuitry coupled to the second transmission line and configured in response to the first logic state of the first control signal to terminate the second transmission line in a second impedance referenced to a second bias voltage for pseudo-differential signaling; and third circuitry for coupling the first circuitry to the second circuitry thus configuring the first and second circuitry as a third impedance termination between the first and second transmission lines in response to a second logic state of the first control signal for true differential signaling. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A data processing system comprising:
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a central processing unit (CPU); a random access memory (RAM); an input output (I/O) interface unit; and a bus for coupling the CPU, RAM and I/O interface unit, the data processing system having a termination network for configuring the termination of first and second adjacent transmission lines for either two data line pseudo-differential signaling or single data line true differential signaling having first circuitry coupled to the first transmission line and configured in response to a first logic state of a first control signal to terminate the first transmission line in a first impedance referenced to a first bias voltage for pseudo-differential signaling, second circuitry coupled to the second transmission line and configured in response to the first logic state of the first control signal to terminate the second transmission line in a second impedance referenced to a second bias voltage for pseudo-differential signaling, and third circuitry for coupling the first circuitry to the second circuitry thus configuring the first and second circuitry as a third impedance termination between the first and second transmission lines in response to a second logic state of the first control signal for true differential signaling. - View Dependent Claims (17, 18, 19, 20)
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Specification