Low voltage differential signaling systems and methods
First Claim
Patent Images
1. A driver comprising:
- a multiplexer adapted to select from a plurality of reference voltages;
an amplifier, coupled to the multiplexer, adapted to receive the reference voltage selected by the multiplexer and set an offset voltage of the driver based on the reference voltage;
a current source circuit, coupled to the amplifier, adapted to provide an output current for the driver;
a plurality of transistors, coupled to the current source circuit and to a data line, adapted to route the output current to produce a positive differential output voltage or a negative differential output voltage based on a data value on the data line; and
a current limiting circuit, coupled to the plurality of transistors, adapted to limit the output current to a value that provides a desired differential output voltage.
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Abstract
A low voltage differential signaling driver is disclosed that is capable of supporting many different LVDS standards or signal level requirements. The low voltage differential signaling driver has a programmable offset voltage and a programmable differential output voltage, which may be programmed independently.
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Citations
18 Claims
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1. A driver comprising:
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a multiplexer adapted to select from a plurality of reference voltages;
an amplifier, coupled to the multiplexer, adapted to receive the reference voltage selected by the multiplexer and set an offset voltage of the driver based on the reference voltage;
a current source circuit, coupled to the amplifier, adapted to provide an output current for the driver;
a plurality of transistors, coupled to the current source circuit and to a data line, adapted to route the output current to produce a positive differential output voltage or a negative differential output voltage based on a data value on the data line; and
a current limiting circuit, coupled to the plurality of transistors, adapted to limit the output current to a value that provides a desired differential output voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
at least two current paths having transistors that regulate an amount of current flowing through the current path; and
a pass gate, coupled to at least two of the current paths, which receives a control signal that determines whether one of the current paths allows the regulated amount of current to flow through the current path.
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10. The driver of claim 9, farther comprising a memory cell that provides the control signal to the pass gate.
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11. A driver comprising:
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means for selecting one of a plurality of offset voltages;
means for providing a driver current and the selected offset voltage to generate a positive differential voltage or a negative differential voltage based on a data signal; and
means for selecting one of a plurality of values for the driver current to provide a desired differential voltage level for the positive differential voltage and the negative differential voltage. - View Dependent Claims (12, 13, 14, 15)
a multiplexer that selects one of a plurality of reference voltages; and
an amplifier, coupled to the multiplexer, that receives the selected reference voltage and sets an offset voltage based on the selected reference voltage.
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13. The driver of claim 12, wherein the providing means comprises:
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a plurality of parallel transistors to provide the driver current, with the number of parallel transistors selectable;
a first pair of transistors that guide the driver current to generate the positive differential voltage when the data signal is asserted; and
a second pair of transistors that guide the driver current to generate the negative differential voltage when the data signal is deasserted.
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14. The driver of claim 13, wherein the means for selecting one of the plurality of values for the driver current comprises a plurality of parallel current paths, with the number of parallel current paths selectable.
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15. The driver of claim 14, wherein the driver is coupled through a differential wire pair to a receiver to form a low voltage differential signaling system.
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16. A method of providing a plurality of low voltage differential signal levels from a single driver, the method comprising:
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programming a desired offset voltage based on a plurality of selectable reference voltages;
providing a programmable current source and the offset voltage to generate a driver current;
channeling the driver current to provide a positive differential output voltage or a negative differential output voltage based on a value of a data signal; and
limiting the driver current to a specified value to provide a desired value for the positive differential output voltage and the negative differential output voltage. - View Dependent Claims (17, 18)
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Specification