可程式化頻寬之三倍超取樣混合式時脈與資料回復電路

Abstract

近年來，由於有線通訊應用的快速成長，在計算機與網路系統中為了增加晶片間的頻寬，高速的I/O時常被使用。其中接收端內的時脈與資料回復電路(CDR)主要用來重建並還原傳輸端所傳送的資料序列。傳統時脈與資料回復電路經常被視為一個負迴授的控制系統，並根據資料序列相位的移動去調整最佳的時脈輸出相位。 然而，另一種CDR架構稱之為'百葉窗式超取樣時脈與資料回復電路'也經常被使用著，此架構在時脈與輸入的關係中不具有相位追隨的能力。 這兩種架構在抖動容忍度的特性上，不同的抖動頻率區間擁有優點和缺點。基於這樣的論點，我們結合兩種不同架構的時脈與資料回復電路和搭配頻寬切換的機制已達到抖動容忍度的改善，特別是在抖動頻率小於迴路頻寬的區間。 在本論文中，一個可程式化頻寬之三倍超取樣混合式時脈與資料回復電路被提出，其中已回復的資料抖動峰對峰值為99.15UI(88.13ps) @4.5Gb/s。在輸入資料速率為4.5Gb/s 和 PRBS length = 10的條件下，抖動容忍度為 1.2UI@10MHz, 5.5UI@1MHz, 和 35UI@100kHz. 供應電壓為1.1V時，電路總消耗功率為46.2mW，總面積為0.98mm2，使用的技術為 UMC 55nm CMOS製程。

In recent years, applications of wirelan communication have been growing rapidly. Meanwhile, high-speed I/O is used to increase the bandwidth between chips in a computer or network. The clock and data recovery (CDR) circuit is responsible for reconstructing the original transmitter bit-stream at the receiver. The CDR has been viewed as a feedback control system that adjusts its output clock according to the phase movement of the input data in the conventional phase-tracking architecture. However, there is another structure of CDR, blind-oversampling based CDR. This CDR is a feed-forward architecture and thus has no phase-tracking between clock and input data. These two types of CDR have their advantages and disadvantages in jitter tolerance performance with different jitter frequency regions. Based on the point at this issue, we combine these two types of CDR and use the programmable bandwidth to enhance the performance jitter tolerance. So the jitter tolerance will be boosted especially in the jitter frequency regions which are below the loop bandwidth. In our thesis, the 3x-oversampling hybrid clock and data recovery circuit with programmable bandwidth is proposed. The measured peak-to-peak jitter of recovered clock is 99.15mU (88.13ps) and the measured jitter tolerance results are 1.2UI@10MHz, 5.5UI@1MHz, and 35UI@100kHz with 4.5Gb/s data rate and PRBS length = 10, respectively. The power consumption is 46.2mW with 1.1V supply voltage. The total area of chip is 0.98mm2 and this chip is fabricated in the UMC 55nm CMOS technology.