A DC-to-12.5 Gb/s 9.76 mW/Gb/s All-Rate CDR With a Single LC VCO in 90 nm CMOS

Abstract

A dual-lane DC-to-12.5 Gb/s all-rate clock and data recovery (CDR) IC with a single LC voltage-controlled oscillator is fabricated in a 90 nm CMOS. An all-rate clock divider with an asynchronous phase calibration scheme is employed to generate all-rate clock signals without a phase mismatch or duty cycle distortion. The IC features an automatic loop gain control scheme that adjusts the bandwidth of a CDR in the background for optimal bit error rate (BER) performance by monitoring the phase difference between the incoming data and the recovered clock signal. The proposed CDR consumes 244 mW at 12.5 Gb/s under dual-lane operation with an input sensitivity of 12 mV(pp), (diff). The CDR supports referenceless allrate operation with a BER < 10(-12) on PRBS31 and compensates for 20 dB of channel loss using a continuous-time linear equalizer (CTLE), a one-tap decision feedback equalizer (DFE), and a three-tap pre-emphasis filter. The power efficiency of the test chip is 9.76 mW/Gb/s.