Altera Corporation

Doris Po Ching Chan

Thungoc M Tran

Sergey Yuryevich Shumarayev

Simardeep Maangat

Wilson Wong

Tim Tri Hoang

Tin H Lai

An equalizer circuitry that includes an equalizer stage having a programmable current source is described. In one implementation, the programmable current source cancels voltage offset. Also, in one implementation, the programmable current source is programmable in user mode. Furthermore, in one implementation, the equalizer circuitry includes a plurality of equalizer stages including the equalizer stage having a programmable current source, where the equalizer stage having a programmable current source is a second equalizer stage in the plurality of equalizer stages. Also, in one implementation, the programmable current source includes a plurality of current sources coupled in parallel and a plurality of sets of control switches for controlling the plurality of current sources. Further, in one implementation, each current source of the plurality of current sources includes a transistor and each set of control switches of the plurality of sets of control switches is for controlling a respective current source and includes a pair of transistors for controlling the respective current source.

Offset cancellation in equalizer circuitry

Decision feedback equalizer ('DFE') circuitry bases determination of the coefficients that are used in its various taps on the algebraic sign of the current value of an error signal and prior serial data signal values output by the DFE circuitry. Use of such algebraic sign information (rather than full error signal values) greatly simplifies the circuitry needed to determine the tap coefficients. The DFE circuitry can be adaptive, i.e., such that it automatically adjusts the tap coefficients for changing serial data signal transmission conditions.

Adaptation circuitry and methods for decision feedback equalizers

Equalization of an incoming data signal can be controlled by sampling that signal at times when data values in that signal should be stable ('data samples') and when that signal should be in transition between successive data values that are different ('transition samples'). A transition sample that has been taken between two successive differently valued data samples is compared to a reference value (which can be one of those two data samples). The result of this comparison can be used as part of a determination as to whether to increase or decrease equalization of the incoming data signal.

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Santa Clara, CA, United States of America

Doris Po Ching Chan