3.2 multi-standard 185fsrms 0.3-to-28Gb/s 40dB backplane signal conditioner with adaptive pattern-match 36-Tap DFE and data-rate-adjustment PLL in 28nm CMOS

• Main Authors: Kawamoto, Takashi, Norimatsu, Takayasu, Kogo, Kenji, Yuki, Fumio, Nakajima, Norio, Tsuge, Masatoshi, Usugi, Tatsunori, Hokari, Tomofumi, Koba, Hideki, Komori, Takemasa, Nasu, Junya, Kawamata, Tsuneo, Ito, Yuichi, Umai, Seiichi, Kumazawa, Jun, Kurahashi, Hiroaki, Muto, Takashi, Yamashita, Takeo, Hasegawa, Masatoshi, Higeta, Keiichi
• Format: Conference Proceeding
• Language: English
• Subjects: Backplanes; Bit error rate; CMOS integrated circuits; Connectors; Decision feedback equalizers; Jitter; Reflection
• ISSN: 0193-6530; 2376-8606
• DOI: 10.1109/ISSCC.2015.7062922

As processing and network speeds are accelerated to support data-rich services, the bandwidth of backplane interconnects needs to be increased while maintaining the channel length and multi-rate links. However, channel losses and impedance discontinuities increase at high data-rates, making it difficult to compensate the channel. In this work, we target serial links from auto-negotiation in 100G-KR4 of 0.3Gb/s to 32GFC of 28.05Gb/s in 40dB backplane architecture. To achieve this challenge, there are two key techniques. First, we introduce a 36-tap decision-feedback equalizer (DFE) to cancel reflections due to connectors because these reflections close the eye. To operate the 36-tap DFE, we need to fix a CDR lock-point and calculate 36-tap coefficients accurately. Thus, we develop a pattern-captured CDR with a 4b pattern filter to fix the lock-point, and a 3b pattern-matched adaptive equalizer (AEQ) to optimize 36 tap coefficients. These techniques enable our chip to compensate 40dB channel loss. Second, we target 100G-KR4/40G-KR4/10G-KR/25G-KR and 32GFC/16GFC/8GFC/4GFC. To operate across a wide range of data-rates, from 0.3 to 28.05Gb/s, with low jitter, we develop a PLL architecture with two LC-VCOs and one ring VCO with a data-rate-adjustment technique by controlling an LDO. Our test chip is fabricated in 28nm CMOS. Our signal conditioner is the demonstration to achieve the BER