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Redriver with output receiver detection that mirrors detected termination on output to input

  • US 8,212,587 B2
  • Filed: 10/23/2008
  • Issued: 07/03/2012
  • Est. Priority Date: 10/23/2008
  • Status: Active Grant
First Claim
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1. A redriver device comprising:

  • a differential input including a true differential input and a complement differential input, the true and complement differential inputs being driven to opposite states by a remote transmitter transmitting data;

    a differential output including a true differential output and a complement differential output, the true and complement differential outputs being driven to opposite states by the redriver device when re-transmitting data to a remote receiver;

    a differential redriving circuit, coupled to the differential input, for re-driving data sent by the remote transmitter onto the differential output as re-transmitted data; and

    an output detector, coupled to the differential output, for detecting a far-end termination on the remote receiver and activating a detect signal in response to detection of the far-end termination;

    a true switched input termination resistor, coupled to the true differential input in response to the detect signal being activated, and disconnected from the true differential input in response to the detect signal not being activated; and

    a complement switched input termination resistor, coupled to the complement differential input in response to the detect signal being activated, and disconnected from the complement differential input in response to the detect signal not being activated;

    wherein the true switched input termination resistor and the complement switched input termination resistor provide termination to the remote transmitter when the output detector detects the far-end termination on the remote receiver;

    wherein the differential redriving circuit further comprises;

    an equalizer that shapes a waveform of the data received over the differential input to generate equalized data;

    a pre-driver that receives the equalized data from the equalizer and generates buffered data;

    an output stage that receives the buffered data from the pre-driver and drives current onto the true differential output and onto the complement differential output;

    wherein the differential output comprises a true line and a complement line that are driven by the differential redriving circuit in opposite directions to indicate data in the re-driven signal;

    a first external coupling capacitor coupled between the differential redriving circuit and the remote receiver on the true line of the differential output; and

    a second external coupling capacitor coupled between the differential redriving circuit and the remote receiver on the complement line of the differential output;

    wherein the first external coupling capacitor prevents D.C. current flow on the true line between the redriver device and the remote receiver;

    wherein the second external coupling capacitor prevents D.C. current flow on the complement line between the redriver device and the remote receiver,whereby the far-end termination on the remote receiver is detected by the redriver device and whereby the far-end termination on the remote receiver is mirrored to the remote transmitter by the true switched input termination resistor and the complement switched input termination resistor on the differential input of the redriver device.

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