适用于4通道100 Gbps SerDes的两级架构正交12.5 GHz低功耗低抖动时钟发生器

为了缓解多通道SerDes中高频时钟信号在长距离传输中引入的噪声过大和功耗过高的问题，设计了一种应用于多通道的低功耗低抖动两级锁相环结构；同时为了进一步降低噪声性能，在第2级锁相环中设计了一种采样鉴相器。该设计将第1级LC振荡器锁相环产生的低频时钟信号（3.125 GHz）传输到各通道收发机后，将该信号作为第2级参考信号，再采用小面积的环形振荡器锁相环产生正交的高频时钟 (12.5 GHz)，这种结构降低了高频时钟在片上长距离传输的距离，提高了收发机的时钟质量；此外该技术避免了使用高频缓冲器，降低了功耗。其中第2级锁相环通过无分频鉴相技术提高了第2级环振锁相环的噪声性能。该时钟发生器电路整体功耗为100 mW，第1级锁相环相位噪声拟合后为-115 dBc/Hz，第2级环形振荡器电路在1 MHz处相位噪声为-79 dBc/Hz，锁相环电路产生的时钟信号整体抖动为2.7 ps。正交时钟偏差在300 fs以内。相比传统时钟发生器，该设计性能有较大提高，功耗有明显降低，适合应用于100 Gbps SerDes中。

A 12.5 GHz Clock Generator Applicable for 4 Way 100 Gbps High Speed Serial Interface Circuits

In order to alleviate the problem of excessive noise and excessive power consumption introduced by long distance transmission of high frequency clock signals in multi channel SerDes, a low power low jitter two stage phase locked loop applied to multi channel serial interface is designed, Simultaneously, this design is used to transmit the low frequency clock signal (3.125 GHz) generated by the first stage LC oscillator phase locked loop to each channel transceiver, this signal is taken as the second level reference signal, and then a small area ring oscillator phase locked loop is used to produce an orthogonal high frequency clock (12.5 GHz). This structure reduces the distance that the high frequency clock transmits over long distances on the chip, and improves the clock quality of the transceiver. In addition, this technology avoids the use of high frequency buffers and reduces power consumption. In order to further reduce the noise performance, a sampling phase detector is designed in the second stage phase locked loop. This technology improves the noise performance of the second stage ring vibration phase locked loop by means of no frequency phase discrimination. The overall power consumption of the clock generator circuit is 100 mW, the phase noise of the first stage phase locked loop is -125 dBc/Hz, and the phase noise of the second stage ring oscillator circuit is -79 dBc/Hz at 1MHz. The overall jitter of the clock signal generated by the circuit is 2.7 ps. The quadrature clock skew is within 300 fs.