Programmable current output and common-mode voltage buffer
First Claim
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1. A programmable logic device having a buffer, the buffer comprising:
- at least one controlled current source;
at least one input node adapted to receive at least one input signal;
first and second output nodes adapted to present first and second output signals;
a detector adapted to generate a sampled voltage corresponding to a common-mode voltage of the output nodes;
a controlled voltage source adapted to generate a common-mode reference voltage; and
,an amplifier adapted to adjust the at least one controlled current source in response to the sampled voltage and the common-mode reference voltage,wherein;
the controlled voltage source is controlled independently of the at least one controlled current source; and
the at least one controlled current source and the controlled voltage source are adapted to be programmably controlled and are each independently programmable; and
wherein the programmably controlled voltage source comprises;
a reference voltage source adapted to produce a reference voltage;
a voltage divider, coupled to the reference voltage source, adapted to produce a plurality of output voltages; and
a plurality of switches adapted to selectively couple one of the plurality of voltages from the voltage divider to an output node,wherein a signal on the output node is the common-mode reference voltage.
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Abstract
A buffer for a programmable logic device has programmable current sink and source circuitry and an independently programmable common-mode voltage reference source. An amplifier, responsive to a common-mode voltage detector and the voltage reference source, forces a common-mode voltage of an output signal from the buffer to approximate the voltage from the common-mode voltage reference source.
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Citations
17 Claims
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1. A programmable logic device having a buffer, the buffer comprising:
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at least one controlled current source; at least one input node adapted to receive at least one input signal; first and second output nodes adapted to present first and second output signals; a detector adapted to generate a sampled voltage corresponding to a common-mode voltage of the output nodes; a controlled voltage source adapted to generate a common-mode reference voltage; and
,an amplifier adapted to adjust the at least one controlled current source in response to the sampled voltage and the common-mode reference voltage, wherein; the controlled voltage source is controlled independently of the at least one controlled current source; and the at least one controlled current source and the controlled voltage source are adapted to be programmably controlled and are each independently programmable; and wherein the programmably controlled voltage source comprises; a reference voltage source adapted to produce a reference voltage; a voltage divider, coupled to the reference voltage source, adapted to produce a plurality of output voltages; and a plurality of switches adapted to selectively couple one of the plurality of voltages from the voltage divider to an output node, wherein a signal on the output node is the common-mode reference voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A programmable logic device having a buffer, the buffer comprising:
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at least one controlled current source; at least one input node adapted to receive at least one input signal; first and second output nodes adapted to present first and second output signals; a detector adapted to generate a sampled voltage corresponding to a common-mode voltage of the output nodes; a controlled voltage source adapted to generate a common-mode reference voltage; and an amplifier adapted to adjust the at least one controlled current source in response to the sampled voltage and the common-mode reference voltage, wherein; the controlled voltage source is controlled independently of the at least one controlled current source; and the at least one controlled current source and the controlled voltage source are adapted to be programmably controlled and are each independently programmable, wherein the at least one programmably controlled current source comprises a first plurality of programmably controlled current sources connected in parallel and programmably controllable such that at least two of the parallel current sources are selected at the same time.
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13. A programmable logic device having a buffer, the buffer comprising:
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at least one controlled current source; at least one input node adapted to receive at least one input signal; first and second output nodes adapted to present first and second output signals; a detector adapted to generate a sampled voltage corresponding to a common-mode voltage of the output nodes; a controlled voltage source adapted to generate a common-mode reference voltage; and
,an amplifier adapted to adjust the at least one controlled current source in response to the sampled voltage and the common-mode reference voltage, wherein; the controlled voltage source is controlled independently of the at least one controlled current source; and the at least one controlled current source and the controlled voltage source are adapted to be programmably controlled and are each independently programmable, wherein; the at least one programmably controlled current source comprises at least first, second, and third programmably controlled current sources, each having a gate, connected in parallel; a first switch connected between the gates of the first and second parallel current sources; and a second switch connected between the gates of the second and third parallel current sources.
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14. A programmable logic device having a buffer, the buffer comprising:
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at least one controlled current source; at least one input node adapted to receive at least one input signal; first and second output nodes adapted to present first and second output signals; a detector adapted to generate a sampled voltage corresponding to a common-mode voltage of the output nodes; a controlled voltage source adapted to generate a common-mode reference voltage; and
,an amplifier adapted to adjust the at least one controlled current source in response to the sampled voltage and the common-mode reference voltage, wherein; the controlled voltage source is controlled independently of the at least one controlled current source; and the at least one controlled current source and the controlled voltage source are adapted to be programmably controlled and are each independently programmable, wherein the output of the amplifier is connected to the gate of an additional current source connected in parallel to the at least one programmably controlled current source.
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15. A programmable logic device having a buffer, the buffer comprising:
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at least one controlled current source; at least one input node adapted to receive at least one input signal; first and second output nodes adapted to present first and second output signals; a detector adapted to generate a sampled voltage corresponding to a common-mode voltage of the output nodes; a controlled voltage source adapted to generate a common-mode reference voltage; and
,an amplifier adapted to adjust the at least one controlled current source in response to the sampled voltage and the common-mode reference voltage, wherein; the controlled voltage source is controlled independently of the at least one controlled current source; and the at least one controlled current source and the controlled voltage source are adapted to be programmably controlled and are each independently programmable, wherein the buffer further comprises; first and second input nodes adapted to receive first and second input signals; a first pair of transistors connected in series at the first output node; and a second pair of transistors connected in series at the second output node, wherein; the first input node is connected to apply the first input signal to the gates of the first pair of series-connected transistors; and the second input node is connected to apply the second input signal to the gates of the second pair of series-connected transistors. - View Dependent Claims (16)
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17. A programmable logic device having a buffer, the buffer comprising:
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at least one controlled current source; at least one input node adapted to receive at least one input signal; first and second output nodes adapted to present first and second output signals; a detector adapted to generate a sampled voltage corresponding to a common-mode voltage of the output nodes; a controlled voltage source adapted to generate a common-mode reference voltage; and
,an amplifier adapted to adjust the at least one controlled current source in response to the sampled voltage and the common-mode reference voltage, wherein; the controlled voltage source is controlled independently of the at least one controlled current source; and the at least one controlled current source and the controlled voltage source are adapted to be programmably controlled and are each independently programmable, wherein the programmable controlled voltage source comprises a voltage divider coupled to a reference voltage source and adapted to produce a plurality of output voltages, wherein the voltage divider supplies the plurality of different voltages to the output node.
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Specification