Serdes voltage-mode driver with skew correction
First Claim
1. A driver circuit for driving data values on a differential output including a positive output node and a negative output node, the driver circuit comprising:
- a voltage-mode driver module configured to drive voltages on the positive output node and the negative output node based on values on a data input of the voltage-mode driver module; and
a first current-mode driver module including;
a head current source operable to source a first current;
a tail current source operable to sink a second current; and
switches configured to selectively couple the head current source to the negative output node and the tail current source to the positive output node or couple the head current source to the positive output node and the tail current source to the negative output node based on values on a data input of the first current-mode driver module,wherein the magnitudes of the first current and the second current are independently selectable.
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Abstract
A driver circuit for transmitting serial data on a communication link combines voltage-mode and current-mode drivers. The driver circuit uses a voltage-mode driver as the main output driver. One or more auxiliary current-mode drivers are connected in parallel with the voltage-mode driver to adjust the output signal by injecting currents into the outputs. The voltage-mode driver supplies most of the output drive. Thus, the output driver circuit can provide the power efficiency benefits associated with voltage-mode drivers. The current-mode drivers can provide, for example, pre-emphasis, level adjustment, skew compensation, and other modifications of the output signals. Thus, the driver circuit can also provide the signal adjustment abilities associated with current-mode drivers.
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Citations
27 Claims
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1. A driver circuit for driving data values on a differential output including a positive output node and a negative output node, the driver circuit comprising:
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a voltage-mode driver module configured to drive voltages on the positive output node and the negative output node based on values on a data input of the voltage-mode driver module; and a first current-mode driver module including; a head current source operable to source a first current; a tail current source operable to sink a second current; and switches configured to selectively couple the head current source to the negative output node and the tail current source to the positive output node or couple the head current source to the positive output node and the tail current source to the negative output node based on values on a data input of the first current-mode driver module, wherein the magnitudes of the first current and the second current are independently selectable. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for driving a serial data signal on a communication link, the method comprising:
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driving the communication link using a voltage-mode driver module having differential outputs coupled to a positive output node and a negative output node, wherein the voltage-mode driver module is configured to drive voltages on the outputs based on values on a data input of the voltage-mode driver module; driving the communication link using a current-mode driver module having outputs coupled to the positive output node and the negative output node, wherein the current-mode driver module is operable to selectively couple a head current source and a tail current source to the positive output node and the negative output node; and selecting currents of the head current source and the tail current source based at least in part on correcting skew on the positive output node and the negative output node. - View Dependent Claims (13, 14, 15, 16)
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17. A driver circuit, comprising:
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means for driving voltages on a differential output including a positive output node and a negative output node, wherein the driven voltages are based on values on a data input of the means for driving voltages circuit; and means for driving currents on the differential output, including; a head current source operable to source a first current; a tail current source operable to sink a second current; and switches configured to selectively couple the head current source to the negative output node and the tail current source to the positive output node or couple the head current source to the positive output node and the tail current source to the negative output node based on values on a data input of the means for driving currents, wherein the magnitudes of the first current and the second current are independently selectable. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification