| Title |
A Full-digital Symbol Rate Estimation Method for an On-die ADC-based Asynchronous PAM-4 Link Eye Monitor |
| Authors |
노성원(Sungwon Roh) ; 김진태(Jintae Kim) |
| DOI |
https://doi.org/10.5573/ieie.2021.58.9.3 |
| Keywords |
High-speed serial links; Eye-diagram; Eye monitor; ADC based eye monitor |
| Abstract |
In this paper, we present an asynchronous on-die eye monitor based on a wideband ADC for high-speed serial link as well as a new method of estimating symbol frequency with a software-based eye diagram reconstruction. The on-die eye monitor is often used to check the signal quality, which is very important to secure low-enough BER(Bit-Error Rate) for high-speed serial links. Compared to previous eye monitors which can only carry NRZ data stream, the proposed eye monitor can measure signal quality with incoming PAM-4 data stream. Moreover, we propose a new method of estimating symbol frequency that improves the frequency estimation error using the linear correlation between the output of estimation circuit and symbol frequency. The average symbol frequency estimation error obtained from behavioral simulation reduces from 0.8198% to 0.0272% by using the proposed method. Therefore, we can estimate frequency more precisely by using the new method. We verified the operation of proposed eye monitor circuit designed in 28nm CMOS using SPICE simulations. The full eye monitor consumes about 9.3mW when running with 56Gbps PAM-4 input stream, which is very low compared to the power consumption of the full 56Gbps receivers that are published recently. |