ADAPTIVE TERMINATION TUNING WITH BIASED PHASE DETECTOR IN A SERDES RECEIVER

摘要

Described embodiments provide for, in a SerDes device, an adaptation process that adjusts termination impedance automatically to obtain a tuned termination. The termination adaptation is realized with a ‘biased’ bang-bang phase detector (BBPD) that biases the weights applied to UP and DOWN outputs of the phase detector. Through an optimization process, the system locks to data eye corners, and thereby is able to optimize termination though a predetermined criteria, such as signal to noise ratio (SNR), horizontal eye (H-) margin, vertical eye (V-) margin or joint SNR and H-/V-margin optimization. As part of the receiver equalization, adaptive termination tuning is performed after the SerDes receiver (RX) path is initially powered-up by tuning the termination above and below its current initial setting and performing the optimization process.

主权项

1. A method of tuning an impedance in a receiver device, the method comprising:
initializing one or more initial termination settings of front-end circuitry impedance to an initial termination set for a predefined input of impedance value; performing a recursive sweep over one or more termination settings to generate a set of recorded margins, the performing a recursive sweep including at each iteration:
generating a data eye from an input signal to a decision device, the input signal including a sequence of data symbols, the data eye including edges including a first inner edge and a second inner edge;performing phase detection, by at least one biased phase detector, of at least two edges of the data eye, wherein the at least one biased phase detector is at least one bang-bang phase detector (BBPD);generating a margin corresponding to at least one particular setting of one or more current termination settings of a settled phase based on a predefined criteria;recording the margin corresponding to the at least one particular setting of the one or more current termination settings of the settled phase; andupdating the one or more current termination settings; determining, when the recursive sweep is complete, a channel impedance-matched set of the one or more termination settings from the set of recorded margins; and adjusting the one or more initial termination settings of front-end circuitry impedance to the channel impedance-matched set.