An On-Chip Monitoring Circuit for Signal-Integrity Analysis of 8-Gb/s Chip-to-Chip Interfaces With Source-Synchronous Clock

Abstract

This paper presents an on-chip monitoring circuit (OCMC) for analyzing the signal integrity of highspeed signals for a chip-to-chip interface with a source-synchronous clocking scheme. The proposed OCMC consists of a fractional-N phase-locked loop (PLL)-based frequency synthesizer, a high-bandwidth track-and-hold circuit, and a 10-bit analog-to-digital converter (ADC) to implement a subsampling scheme. The proposed fractional-N PLL-based frequency synthesizer improves the time jitter accumulated in a voltage-controlled oscillator using a fractional frequency divider operated by an eight-phase clock. The bandwidth of the track-and-hold circuit is designed to be 6 GHz, using inductive peaking realized through a source follower. The OCMC samples 49 points over two unit intervals of a high-speed input signal when the frequency multiplication of the frequency synthesizer is 6.125/6. The 10-bit ADC uses the architecture of a pipelined successive approximation register ADC to reduce the power consumption and chip area. The proposed OCMC is implemented with 65-nm CMOS technology and a 1.2 V supply. The 8-Gb/s chip-to-chip interface signal is reconstructed with time and voltage resolutions of 5.1 ps and 1.17 mV, respectively.