SiGe BiCMOS PAM-4 Clock and Data Recovery Circuit for High-Speed Serial Communications

A multilevel clock and data recovery (CDR) circuit for highspeed serial data transmission was designed using the IBM 6HP 0.25 μm SiGe BiCMOS process technology. The circuit extracts the clock from a 32 Gb/s 4-level pulse amplitude modulated (PAM-4) input signal and outputs four channels of retimed NRZ data at 8 Gb/s per channel. The CDR design incorporates a PAM-4 to 2-bit-binary converter, a phase/frequency detector, a loop filter, a quadrature LC ring oscillator and a data-retiming module. The circuit operates using a 3.3V supply voltage with a 350mA current consumption. The simulation results show that the peak-to-peak jitter is 1.3 ps, the capture range is 2 GHz, the acquisition time is 200 ns and the input sensitivity is 150 mV. This PAM-based CDR technique is quite suitable for low-loss transmission channels such as fiber optic communications or short-distance copper links, including network-on-chip (NOC) implementations and storage area networks (SANs).